Summary - lecture 5, 7, 8, 10, 11 PDF

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Summary

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Central Nervous System Label the brain

Frontal Lobe Thalamus Amygdala Cerebellum Pons Brainstem

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The brain is divided into two half, called cerebral hemispheres (right and left) There is a prominent groove, in the middle of the brain called the longitudinal fissure The fold of tissues called the gyrus and the grooves between them called sulci

Cerebral Hemispheres  

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Prominent part of brain Cerebral hemispheres control the opposite side of the body  Right cerebral hemisphere is responsible for controlling the left side of the body  Left cerebral hemisphere is responsible for controlling the right side of the body Surface convoluted  Elevated ridges gyri  Shallow grooves sulci Fissures- groove separating larger regions In general each hemisphere controls the opposite side of the body-major fibre tracts decussate (cross the midline) Each hemisphere composed of several lobe  Frontal lobe  Parietal lobe  Temporal lobe  Occipital lobe Frontal Lobe Frontal Lobe

Frontal Lobe

Occipital Lobe

The peripheral nervous system Structure of peripheral nerves What is a neuron? ● Nerve cell Two types of processes that can extend from the cell bodies of neurons: ● axons and dendrites

Different functional types of neuron: ● Afferent – GSA, GVA ● Efferent – GSE, GVE ● Interneurons What is the difference between a nerve fibre and a nerve? ● Nerve fibre- the long process of a neuron ● Nerve – a collection of nerve fibres

Structure of a nerve: What do we know about nerve fibre? ● Neurons normally transmit impulses in one direction only ➢ GSA fibre transmits towards the CNS ➢ GSE fibre transmits towards the PNS- to muscles Can a nerve transmit information in both directions? ● The function of a nerve is the sum total of the functions of the individual axons which it contains

Structure of a peripheral nerve: ● Composed of many nerve fibre ● Arranged in bundles = fascicles ● Each bundle separated by connective tissue ● Blood vessels run in the connective tissue between the fascicles to supply the nerve fibres ● Bundles of fascicles surrounded by connective tissue to make a nerve (bound together) Connective tissue layers ● Endoneurium: surrounds each nerve fibre ● Perineuruim: binds groups of fibres into fascicles ● Epineurium: surrounds the whole nerve Schwann cells ● Cells that protect the axon, by wrapping around the axon ● Found in the PNS ● May wrap many times around the axon ➢ Forms myelin sheath ➢ Nerve fibre is referred to as myelinated ➢ Enables faster transmission of action potentials ● Axons may be embedded in Schwann cell ➢ No myelin sheath ➢ Referred to as unmyelinated

➢ Slower transmission of action potential

Cut crossed the nerve and look at different structures Example of myelinated fibre: where the Schwan cell wrapped around Example of unmyelinated fibre: where the axon is push into the Schwan cell Three fascicles bound by epineurium Can see blood vessels running between the fascicles to supply the nerve fibre

Branching of Peripheral nerves Nerve branch A typical peripheral nerve may have branches to supply: ➢ ➢ ➢ ➢

Skin (cutaneous) Skeletal muscle (muscular) Tissues of a joint (articular) Major blood vessels (vascular)

Nerve fibres in branches of peripheral nerves What does the muscular branch of a peripheral nerve innervate? ● Skeletal muscle Consider a nerve that is found in the thigh ● A muscular branch would innervate muscles of the though Therefore fibre types present would be: ● GSE- to skeletal muscle- to cause contraction ● GSA- from the skeletal muscle stretch ● GVE- to the smooth muscle in the blood vessels supplying the muscle

What type of fibres found in a cutaneous branch (eg: innervating the skin over the anterior surface of the thigh?) ● GSA- carrying sensory information from the skin, eg: temperature, pain ● GVE- innervating smooth muscle in the skin ➢ The small muscles that move the hairs in the skin (arrector pili muscle) ➢ Sweat glands ➢ Smooth muscle in the walls of blood vessels

Spinal Nerves Formation of a spinal nerve ● Inside the vertebral canal is the spinal cord ● Outside the vertebral canal is the spinal nerve

How do we form a spinal nerve? ● Each spinal nerve connects to the spinal cord by a dorsal root and a ventral root ● The roots are made up of small rootlets, all the information coming from one spinal segment will combine to make a root. ● Ventral root carries all the motor information ● The dorsal root carries sensory information back into the spinal cord ● The dorsal root is swollen because the cell body of the sensory neurons lied outside the spinal cord in a ganglion ● Dorsal root and ventral root combined together to make a spinal nerve

Branching of spinal nerves The spinal nerve then divides into a usually smaller dorsal (=posterior) primary ramus and a larger ventral (=anterior) primary ramus

● the ventral root will supply the side of the body and the anterior of the body and the limbs ● All spinal nerves divide into posterior and anterior rami ➢ Posterior (dorsal) rami supply the structures of the back ➢ Anterior (ventral) primary rami supply all other somatic structures including limbs How does nerve fibers enter and exit a spinal nerve? ● GSE- the cell body located in the ventral horn. ● The cell body in the ventral horn will coming out by rootlets through the ventral root. travelling through the spinal nerve and heading off to the ventral ramus ● GSA- the cell body will come in from the dorsal ramus, travel through the dorsal root, with it cell body in the dorsal root ganglion before it enters the dorsal horns. From there it will be going through an ascending pathway up to the CNS.

Nerve Plexi ● A network or underjoining of nerves by means of numerous communicating branches ● May be somatic or autonomic ● Nerve plexi combine nerve fibres from different sources or levels to form new nerves with specific target or destinations

Somatic nerve plexi ● A limb has many nerves supplying the different tissues and regions of that limb; these arise from a nerve plexus ● A nerve plexus serves to redistribute nerve fibers from several anterior rami into a number of different peripheral nerves in a limb. ● There are Branchial plexus, lumbar plexus and sacral plexus

Autonomic nerve plexus ● Supply internal organs (eg. Heart, lungs, digestive systems) ● Large number of fibres forming different plexi

● Take the motor information to the heart and sensory information away from the heart to the CNS

How do we build a plexus? ● Nerve plexi are formed from the ventral primary rami of spinal nerves ● Each ventral primary ramus divides and interweaves with other rami, finally forming peripheral nerves

Dermatomes and myotomes Spinal segments ● There are 31 pairs of spinal nerves ● Each set of spinal nerves relates to a specific spinal segment

Spinal segments and dermatomes ● Each spinal segment is connected (via its GSA fibres) to the skin in a specific region of the body ● The area of skin innervated by the branches of a single spinal segment is called a Dermatome (“skin segment”) ● This can be used to help locate the injured region of the spinal cord if it has been damaged

Spinal segments and myotomes

● Each spinal segments is connected (via its GSE fibres) to a block of muscle in a specific part of the body ● The block of muscle innervated by the branches of a single spinal segment is called a myotome (“muscle segment”) ● This can also be used to help locate the injured region of the spinal cord if it has been damaged.

Cranial Nerves ● ● ● ● ● ● ●

Part of the PNS 12 paired nerves supply structures of the head and neck numbered of the cranial nerve is rostro-caudally cranial nerves 1 and 2 are attaching to the forebone 3 and 4 are attaching to the midbone 5 down to 12 attached to the hine bone

Nerve Fibre types ● Motor ➢ GSE- General Somatic Efferent (stimulates muscle under conscious control) (eg. to skeletal muscles) ➢ GVE- general Visceral Efferent (stimulates involuntary smooth muscle) (eg. to smooth and cardiac muscles) 

Sensory  GSA- General Somatic Afferent (eg. Touch, pain, temperature, proprioception)  GVA- General Visceral Afferent (eg. Visceral reflexes)  SA- Special Afferent (some cranial nerve) (special senses such as smell, sight, balance, hearing, taste)

Cranial nerve name

#

Name

What is it?

Function

I II III

Olfactory Optic Oculomotor

Sensory Sensory Motor

IV

Trochlear

V

Trigeminal

VI

Abducens

VII

Facial

VIII

Vestibulocochlear

IX

Glossopharyngeal

X

Vagus

XI

Accessory

XII

Hypoglossal

Sense of smell Sense of sight Responsible for innervating (most) the muscle to move the eye Innervating muscle goes through a pulling system Responsible for relaying sensory information from the face Innervating the muscle of mastication (chewing) Innervate the single muscle the lateral rectus Its role is to abduct the eye, which allow you to look side ways Facial nerve, innervate the face (muscle that move the face eg. Smiling) Also responsible for relaying the sense of taste Vestibular system which controls our sense of balance movement and spatial awareness Cochlear refers to the organ of hearing Therefore, responsible for hearing and balance Glosso-tongue Pharyngeal- pharynx Sense of taste and responsible for the back of the tongue and the throat Responsible for lots of things: supplying some of the pharynx, the heart and digestive system Have an extra or supplementary nerve Composed of two parts (cranial and spinal) Originates from the cervical region of the spinal cord ascends into the cranium then descends to leave the cranium via a different hole and supply to the superficial of the neck and back Travels underneath the tongue and supply the muscle that move the tongue

Motor Both

Motor

Both

Sensory

Both

Both Motor

Motor

Nervous Reflex Arcs 

Many bodily responses belong to a response known as a reflex  A reflex is a rapid motor response to a stimulus  They are generally a fast, intrinsic and predictable response to a stimulus  The message does not have to go to the brain to produce a movement

Reflexes  Reflexes can be mediated by the spinal cord (spinal reflex)  Do not require movement from higher (brain) centres, however in many cases the brain is advised of any reflex activity/response  The neural circuitry involved is referred to as a Reflex Arc

Components of a Reflex Arc 1. Receptor: Stimulus 2. Sensory neuron: GSA or GVA 3. Integration centre: i. Monosynaptic – synapse between sensory neuron and motor neuron ii. Polysynaptic – includes interneurons 4. Motor neuron – GSE or GVE 5. Effector: muscle tissue or gland

Example of a Spinal Reflex: The stretch reflex Function of the reflex:  Ensure the muscle stays at its desired length  Important for postural muscle  Effect of the reflex  The muscle will contracts in response to being stretch  Clinical test  Knee jerk reflex, tests spinal levels L2-4  Stimulus- muscle stretch  Afferent (have the cell body in the dorsal root ganglion)- take the impulse of stretch from receptor to our spinal cord (intergration center)  Monosynaptic reflex, therefore it will synapse with an efferent neuron which caused the muscle to contract (an extension of knee joint) 

Example: the withdrawal (or flexor) reflex

Function of reflex  The automatic removal of threatened body part from a stimulus  Elicited by a painful stimulus  Effect of reflex  Withdrawal of the body  Stimulus- pulled on the forearm  Afferent signal being sent to the spinal cord  The interneuron will synapse with our afferent fibres, which travel down to the muscle to cause an effect-withdraw 

Advantages and disadvantages of reflex control, as oppsed to voluntary action, in the organisation of behaviour 

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Advantages  Fast – don’t need to wait for the signal to go up to the brain and send the signal back  Useful- in the case of withdrawal reflex, removing our body from potential threat (eg fire, sharp nails) Disadvantages  Happen regardless of safety (although can be suppressed) Eg: quickly taking something hot out of the oven

Autonomic Nervous System and Special Sense Autonomic Nervous System Peripheral Nervous System (PNS)

Central Nervous System (CNS)

Sensory (afferent) division

Motor (efferent) division

Somatic Nervous System

Autonomic Nervous System (ANS)

Sympathetic division (fight of flight)

Parasympathetic division

Stimulates the body

Calm the body down Autonomic 2 neurons

Somatic ANS Neurons are Different to Somatic Neurons      

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Preganglionic neurons Postganglionic neurons Length of Sympathetic and Parasympathetic neurons is different Cell body location of Sympathetic and Parasympathetic neurons is different Neurotransmitters are sometimes different the parasympathetic division of the ANS has a long preganglionic neuron and a short postganglionic neuron The sympathetic division of the ANS has a short preganglionic neuron and a long postganglionic neuron

Typical Target Tissues Sympathetic   

Visceral organs in body cavities Visceral structures in somatic areas of the body (eg. Glands in the skin) Visceral structures in both the somatic and visceral areas of the body (eg. Smooth muscle in blood vessel walls)

Parasympathetic 

Visceral organs in body cavities

GSA

GSE

CNS Interneuron

General Visceral Efferent (GVE) Nerve Fibres Preganglionic Sympathetic  

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Cell body  Located in the lateral horn of spinal segments T1 – L2 Fibre course (short neuron)  Travel out of spinal cord in ventral root  Pass through white rami communicans (structure associated with sympathetic trunk) Synapse  In sympathetic ganglia

Postganglionic sympathetic  

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Cell body  Located in sympathetic ganglia Fibre course (long neuron)  Pass through grey rami communicans  Enter either dorsal or ventral rami of adjoining spinal nerves  Travel with spinal nerves to their effector or target organ Synapse  Directly onto effector organ (eg: smooth muscle)

Preganglionic Parasympathetic  

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Cell body  Grey matter of brainstem or grey matter of spinal segments S2-S4 Fibre course (long neuron)  For brainstem cell bodies-CN 3, CN 7, CN 9, CN 10  For sacral spinal segment cell bodies- ventral roots of sacral spinal nerves and pelvic nerves Synapse  In parasympathetic ganglia  Near the organ or structure they will innervate

Postganglionic Parasympathetic   

Cell body  Located in parasympathetic ganglia Fibre course (short neuron)  Pathway from ganglia to effector or target Synapse  Directly onto effector organ (eg. Smooth muscle)

Outflow Definition 

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Thoracolumbar outflow  Relates to origin of sympathetic neurons  These neurons arise in the thoracic and lumbar regions of the spinal cord Craniosacral outflow  Relates to origin of parasympathetic neurons  These neurons arise in the brainstem or in the sacral region of the spinal cord

Neurotransmitters in ANS

 Cause contraction in skeletal muscle  In the sympathetic system the preganglionic neuron synapse to the postganglionic neuron and the postganglionic neuron then travel towards the smooth muscle target and release norepinephrine (NE) neurotransmitter  The parasympathetic postganglionic neuron releases acetylcholine (Ach)

Neurotransmitter Receptors Introduction to pharmacology Two different types receptor subtypes can respond to the same neurotransmitter, but respond differently to drugs  

Neurotransmitter = acetylcholine (Ach) Two types of receptors  Nicotinic Receptor  Somatic neuromuscular junctions (skeletal muscle)  Autonomic ganglia  Muscarinic receptor  Parasympathetic postganglionic-smooth muscle junction

Two major classes of Adrenergic receptors  

Alpha (α) receptors  Two subtypes Beta (β) receptors  Three subtypes

Important summary 

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Preganglionic -> Postganglionic synapse  Nicotinic receptor  Both true for Sympathetic and Parasympathetic Postganglionic  Sympathetic nervous system  Release noradrenalin  α or β receptors  parasympathetic nervous system  Ach  Muscarinic receptors

Sympathetic trunk/ chain      

Sympathetic pre-ganglionic fibres arise from spinal segments ( T1-L2) Pre-ganglionic sympathetic fibres pass through white rami comminicans to enter adjoining sympathetic trunk ganglion These ganglia join up to form the sympathetic trunk The sympathetic trunk extends from the neck to the pelvis Post-ganglionic sympathetic fibres leave the sympathetic trunk by gray rami communicans They enter the ventral or dorsal ramus of adjoining spinal nerves

Importance of the Sympathetic Trunk   

Sympathetic pre-ganglion fibres arise only from T1-L2 Sympathetic post-ganglion fibres travel from neck to pelvis Therefore, the trunk distributes sympathetic fibres to the whole body as it extends the ‘reach’ of the sympathetic fibres

Hitch-hiking Fibres Hitchhiking means that the nerve fibres travel along paths (existing paths) already created to its final destination

Purpose of Hitch-hiking

Sympathetic pre-ganglionic neurons

 Sympathetic preganglionic neuron cell bodies are located in the spinal cord  Cell bodies of sympathetic postganglionic neurons are located in paravertebral ganglia (chain ganglia) alongside the spinal column  There are sympathetic targets in the face  Pupil dilators  Sweat glands  Blood vessels

Sensory Modalities NP21- special sensation are those associated with specialised receptor organs found only in the head and neck. General sensations are associated with receptor organs distributed throughout the body including the head and neck Refers to characterise different sensory modalities as either ‘general’ or ‘special’ Senses:     

Sight Smell Taste Hearing Touch

Senses (there may be up to 21) Sight Taste Smell Hearing Touch  Temperature (hot/cold)  Touch  Vibration  Pressure  Proprioception (for space) Balance Nociception (pain)

Modality/receptor Light/Photoreceptor Gustaoception Olfaction Sound/ mechanoreceptors

Equilibrioception

Special senses Sight 

Structure of receptor organ  Photoreceptor and bipolar neurons

Special or General Special

Week 10 – Thoracic cavity Thoracic cavity and membranes Structure of the thoracic cavity  

Manubrium sternum

 Esophagus

1st Rib

Jugular notch



T1 Sternum

The upper aperture is the shape of the kidney Allow blood vessels to and from the head and neck The esophagus run down to supply the stomach The trachea comes in and break into the main bronchi, going out to the lungs

True Ribs

Costal margin Anterior surface

Floating Ribs

False Ribs

T12    

The diaphragm sits dome (can be up to T4) on full expira...