Chapter 13 - Human Anatomy and Physiology PDF

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chapter 13-The spinal cord  

04/09/2017

spinal cord anatomy spinal meninges (singular is meninx) 

meninges are 3 protective , connective tissue covering that encircle the spinal cord and brain. Layers include: dura mater, arachnoid mater and pia mater

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spinal cord is protected by cushion of fat and connective tissue located in the epidural space

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epidural space: b/w the dura mater and the wall of the vertebral canal

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dura mater: superficial of the 3 meninges,

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o

forms a sac from the level of the foramen magnum in the occipital bone

o

continuous with the epineurium ( outer covering of spinal and cranial nerve)

arachnoid mater: middle layer, and is deep to the dura mater o

avascular covering the comprised of cell and think collagen and elastic fibers.

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subdural space: space between the dura mater and the arachnoid mater , contains interstitial fluid

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pia mater: innermost layer of think transparent connective tissue layer that adheres to the surface of the spinal cord and brain o

made of bundle of collagen fibers

o

has blood vessels hat supply oxygen and nutrients to the spinal cord

o

subarachnoid space; space between the arachnoid and pia mater , contains shock-absorbing cerebrospinal fluid

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external anatomy of the spinal cord 

spinal cord is oval in shape, flattened slightly anteriorly and posteriorly

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cervical enlargements: is the superior enlargement o

extends from C4 to T1

o

nerves to and from the upper limbs arise from here

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lumbar enlargements: inferior enlargement o

extends from T9-T12

o

nerves to and form lower limbs are from here

conus medullaris: the spinal cord terminates as a tapering concial structure into this o

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ends at the level of the intervertebral disc between L1-L2

filum terminale: arises from the conus medullaris o

is an extension of the pia mater that extends inferiorly, fuses with the arachnoid mater and dura mater

o 

anchors the spinal cord to the coccyx

internal anatomy of the spinal cord 

2 grooves penetrate the white matter of the spinal cord and divide into right and left side as following:

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anterior median fissure: wide groove on the anterior ( ventral) side

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posterior median sulcus: narrow furrow on the posterior (dorsal) side

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gray matter in shaped like and H or butterfly

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gray commissure: forms the crossbar of the H

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central canal: small space at the center of the gray commissure

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o

extends entire length of the spinal cord and is filled with cerebrospinal fluid

o

continuous with the 4th ventricle in the medullar oblongata of the brain

anterior or ventral white commissure: connects the white matter of the right and left side of the spinal cord

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nuclei : cluster of neuronal cell bodies in the gray matter

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gray matter on each side of the spinal cord divides into regions called horns

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posterior (dorsal) gray horn: contains cell bodies and axon of interneurons as well as axons of incoming sensory neurons

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anterior (ventral) gray horn: contain somatic motor neurons that provide nerve impulses for contraction of skeletal muscles

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lateral gray horn: in the thoracic and upper lumbar of the spinal cord o

are cluster of cell bodies of the autonomic motor neurons that regulate the activity of cardiac muscle, smooth muscle and glands

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columns: anterior and posterior gray horns divide the white matter in 3 areas called columns. o

1)anterior (ventral) white column

o

2) posterior (dorsal) white column

o

3)lateral white column

o

each of the above has specific bundles of axon having a common origin or destination and carrying similar information

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tract: the bundles in each column, that extends long distances up or down the spinal cord ,

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sensory (ascending) tract: has axons that conduct nerve impulses toward the brain

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motor (descending) tract: axons that carry nerve impulses from the brain

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Spinal nerves: 

path of communication between the spinal cord and specific region of the body

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There are 31 pairs, 8 cervical (C1-C8) 5 lumbar (L1-L5), 5sacral (S1-S5) Coccygeal ( CO1)

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mixed nerve: spinals nerves that have sensory and motor axons

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Roots: bundles of axon that connect each spinal nerve to a segment of the cord

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Rootlets: smaller bundles of axon, contains sensory axons and motor axon

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posterior or dorsal root: contain sensory axon that conduct impulse from sensory receptors in the skin muscle and internal organs into the central nervous system o

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has a swelling called posterior or dorsal root ganglion

posterior or dorsal root ganglion: had cell bodies of sensory neurons

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anterior or ventral root: contains axon of motor neurons that conduct nerve impulse from the CNS to effectors ( muscle and glands)

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cauda equine: roots of nerves, its means horse’s tail

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Describe the components, connective tissue coverings and branching of a spinal nerve.

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connective tissue coverings 

endoneurium: axons within a nerve are rapped in it , it’s the innermost layer o

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fascicle: groups of axon with their endometrium are held together in bundles by this

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perineurium: middle layer, thicker layer of connective tissue o

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consist of mesh of collagen fibers, fibroblasts and macrophages

consist of fibroblasts and collagen fibers

epineurium: outermost cover over the entire nerve o

consist of fibroblasts and collagen fibers

o

extensions of it fills space between fascicles

distribution of spinal nerves 

spinal nerves divide into several branches which are known as ramus or rami o

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ramus serves the deep muscles and skin of the posterior surface of the trunk

meningeal branch: o

This branch reenters the vertebral cavity through the intervertebral foramen and supplies the vertebrae, vertebral ligaments, blood vessels of the spinal cord, and meninges

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Define the term plexus, and describe the anatomical importance of a plexus.

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Plexus

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Plexus: axons of the ramus form networks on left and right side of the body by joining with various numbers of axon . the network of axon is called plexus

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cervical plexus: formed by roots of C1-C4 , one on each side of the neck o

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supplies the skin and muscles of the head, neck and superior part of the shoulder and chest

brachial plexus: o

C5-C8 and T1 forms it

o

Passes first rib posterior to the clavicle and then enters the axilla

o

Provides the entire nerve supply of the shoulder and upper limbs

lumbar plexus: o

L1-L4 forms it

o

Supplies the anterolateral abdominal wall, external genitals and part of the lower limbs

sacral plexus o

formed by L4-L5, S1-S4

o

is situated anterior to the sacrum

o

supplies the buttocks, perineum and lower limbs ,

o

largest nerve the sciatic nerve arises from it as well

coccygeal plexus o

supplies are of skin in the coccygeal region

o

spinal nerve S4-S5 AND coccygeal nerve make it

intercostal or thoracic nerves o

anterior rami of spinal nerves T2-T12 don’t enter formation of plexus and are known as intercostal nerves

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directly connect structure they supply in the intercostal space

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Describe the clinical significance of dermatomes.

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Dermatome 

Trigeminal nerve serves most of the skin of the face and scalp

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Area of the skin that provides sensory input to the CNS via one pair of the spinal nerve or the Trigeminal nerve

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Describe the functions of the major sensory and motor tracts of the spinal cord.

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spinal cord physiology 

spinal cord has 2 principle functions in maintaining homeostasis : nerve impulse propagation and integration of information

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white matter tracts are for nerve impulse propagation .

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sensory input travels toward the brain and motor output travels from the brain toward skeletal muscle and other effectors

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gray matter: receives and integrates incoming and outgoing information

sensory and motor tracts 

spinal cord conducts nerve impulse

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name of the tact indicates its position in the white matter and where it begins and ends

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for ex. Anterior corticospinal tract : located in the anterior white column, it begins in the cerebral cortex and ends in the spinal cor. Location of axon terminal comes last in the name. o

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because it conveys nerve impulse from brain to spinal cord its motor ( descending)

lateral and anterior spinothalamic tracts 

nerve impulse from sensory receptors move up the spinal cord to the brain along 2 main routes on each side : spinothalamic tract and posterior column

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spinothalamic tract: conveys nerve impulse for sensing pain, warm, cool, itch, tickling, deep pressure and crude touch

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direct motor pathway 

convey nerve impulse that originate in the cerebral cortex and are destined to cause voluntary movements of skeletal muscles

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indirect motor pathways 

These tracts convey nerve impulses from the brain stem to cause automatic movements and help coordinate body movements with visual stimuli.

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Also maintains skeletal muscle tone, sustain contraction of postural muscles, play a major role in balance by regulating muscle tone in response to movements of the head

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Describe the functional components of a reflex arc, and explain the relationship of reflexes to

homeostasis. 

reflex 

spinal reflex: when integration takes place in the spinal cord gray matter

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cranial reflex: when integration occurs in the brain stem rather than the spinal cord

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somatic reflex: involves contraction of skeletal muscle

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autonomic or visceral reflex: involves responses of smooth muscles, cardiac muscle and glands, we are unaware of these reflexes

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reflex arc 

Spinal cord serves as integrating center for some reflexes.

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Reflex is a fast involuntary, unplanned sequence of actions that occurs in response to a particular stimulus o

sensory receptor: respond to a stimuli by producing a generator or receptor potential

o

sensory neuron: axon conduct impulses from receptor to integrating center

o

integrating center: one or more region within the CNS that relay impulses from sensory to motor neurons

o

monosynaptic reflex arc: reflex pathway having only one synapse in the CNS

o

polysynaptic reflex arc: involves more than 2 types of neurons and more than one CNS synapse

o

motor neuron: axon conducts impulse from integrating center to effector

o

effector: muscle or gland that responds to motor impulses

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stretch reflex: causes contraction of a skeletal muscle in response to stretching of the muscle

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muscle spindle: slight stretching of a muscle stimulates sensory receptors in the muscle o

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spindles monitors changes in the length of the muscle

ipsilateral reflex arc: when sensory nerve impulse enters the spinal cord on the same side from which motor nerve impulse leaves it

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muscle tone: small degree of contraction present while the muscle is at rest , this helps avert injury by preventing overstretching

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reciprocal innervation: arrangement in which the components of a neural circuit simultaneously causes contraction of one muscle and relaxation of its antagonist . o

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prevents conflict between the opposing muscle and its vital in coordinating body movements.

tendon reflex 

operates to control muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might be torn

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this reflex can override stretch reflex when tension is great ( makes you drop the heavy object for example)

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tendon organ or Golgi tendon organ o

sensory receptors for tendon reflex

o

detect and respond to changes in muscle tension that are caused by passive stretch or muscular contraction

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flexor or withdrawal reflex: when you step on something and pull away that’s what this reflex is

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intersegmental reflex arc: when impulse from one sensory neuron ascend and descend in the spinal cord and activate interneurons in several segments of the spinal cord. o

Can activate more than one neurons so can stimulate more tan one effector

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crossed extensor reflex: when you step on something painful, this reflex maintains your balance

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contralateral reflex arc: sensory impulse enter on one side of the spinal cord and motor impulse exits on the opposite side o

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cause extension of contralateral limb and withdrawal of stimulated limb

Describe two clinically-important reflexes.

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patellar reflex (knee jerk reflex): extension of the leg at the knee joint by contraction of the quadriceps femoris muscle in response to tapping the patellar ligament o

absent in people with chronic diabetes

o

exaggerated in disease or injury involving certain motor tracts descending from the higher centers of the brain to the spinal cord

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Babinski reflex: results from stroking of the lateral outer margin of the sole o

Great toe extends with or without a lateral fanning of the other toes

o

In kids under 1 ½, more than this age indicates interruption of the corticospinal tract as the result of a lesion of the tract ,

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disorders 

shingles: acute infection of the peripheral nervous system caused by herpes zoster o

when the reactivated virus overcomes a wakened immune, leaves the ganglion and travels down sensory neurons of the skin by fast axonal transport

o

results in pain, discoloration of the skin, characteristic line of skin blisters

o

line of blister marks the dermatome of the particular cutaneous sensory nerve belonging to the infected posterior root ganglion

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poliomyelitis o

known as polio, caused by poliovirus

o

marked by fever, headache, stiff neck and back, deep muscle pain and weakness, loss of certain somatic reflexes

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o

most serious form, produce paralysis by destroying cell bodies of motor neurons

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can cause death from respiratory or heart failure

04/09/2017 

chapter 15

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ANS neurotransmitters and receptors 

autonomic neurons are classified as either cholinergic or adrenergic

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Receptors for he neurotransmitter are integral membrane protein located in he plasma membrane of the postsynaptic neurons or effector cell

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Cholinergic neurons and receptors 

Release the neurotransmitter ACH ( acetylcholine)

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Neurons include the (1) all sympathetic and parasympathetic preganglionic neurons, (2) sympathetic postganglionic neurons that innervate most sweat glands, and (3) all parasympathetic postganglionic neurons

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Cholinergic receptors: integral membrane protein in the post synaptic plasma membrane o

2 types are nicotine receptors and muscarinic receptors

o

Nicotine receptors: are in plasma membrane of dendrites and cell bodies of both sympathetic and parasympathetic postganglionic neurons , in the motor end plate at the neuromuscular junction

o 

Mimics the action of ACH by binding to these receptors

Muscarinic receptors: present in plasma membrane of al effectors and innervated by parasympathetic postganglionic axon

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ACH doesn’t activate either of them

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ACH is inactivated by the enzyme Acetylcholinesterase (AChE)

04/09/2017 

CHAPTER 17

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Describe the retinal processing of visual input and the neural pathway of nerve impulses from the retina to

the brain.  

brain pathway and visual fields 

axon within the optic (2) nerve pass through the optic chiasm

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optic chiasm: a crossing point of the optic nerves

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optic tract: after passing the optic chiasm, axon become part of this tract o

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optic radiations: projects to the primary visual are in the occipital lobes of the cerebral cortex , o

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after the axon enter the brain and most of them terminate in the thalamus

axon synapse with neurons whose axon form optic radiations

visual field: everything that can be seen by ones eye o

because our eyes are located anteriorly, the visual field overlaps considerably

o

divided into 2 regions : nasal central half and temporal or peripheral half

o

light rays from an object in the nasal half of the visual field fall on the temporal half of the retina

o

light rays from object in the temporal half of the visual field fall on the nasal half of the retina

o 

binocular visual field 

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visual info from right side of each visual field conveyed to the left and vice versa

where the visual field of 2 eyes overlap...