*Peripheral Nervous System - Google Docs PDF

Preview

Summary

Download *Peripheral Nervous System - Google Docs PDF

Description

Components of the Peripheral Nervous System  Sensory Receptors- ending of neurons or separate, specialized cells that detect things such as temp, pain, etc.   Nerves- a bundle of axons and their sheaths the connect to the CNS to sensory receptors, muscles, and glands.  ● Two divisions:  ○ Cranial nerves- originate or terminate from the brain; 12 pairs (bilateral, all nerves have a left and a right side)  ○ Spinal nerves- Originate or terminate from the spinal cord; 31 pair  Ganglions- collections of neuron cell bodies outside the CNS ● The area where you have all the cell bodies of the nerve and they are outside the CNS is known as a ganglion.  ● Many of the cells bodies of the PNS are inside the CNS.   ● All sensory information from spinal nerves are going to have their neuron cell bodies in the ganglion,   Plexus- extensive network of axons, and sometimes neuron cell bodies, located outside CNS ● Basically a network of nerves where we can exchange information from one level of spinal cord to another.   

Divisions of the PNS ● Divided into two divisions 1. Sensory (afferent)- transmits action potentials from receptors to CNS  ● Taking information from the internal and external environment and bring it back to the CNS  ● Information is carried via electrical signals called action potentials 

● Action potentials get created by sensory information/stimuli from the environment triggering the receptors that detect those changes. This creates an action potential that gets sent back to the central nervous system.   ● After the action potential gets to the central nervous system, it creates then a motor response 2. Motor (efferent)- transmits action potentials from CNS to effectors, muscles and glands  ● Retakes the action potential from the central nervous system and we go out to what we called the effector tissues  Effector tissues are muscles in the body or glands, it's basically the target tissue of the motor signal ● There are three main different muscle types,   ○ Skeletal muscle  ● The ones that move your bone. Create movement.  ○ Cardiac muscles   ● Heart muscle  ○ Smooth muscle  ● Muscles you can't control consciously (muscle around digestion system organs etc...)  ● Two types of glands   ○ Exocrine  ○ Endocrine   ● The motor side is divided into two sections;  Somatic nervous system- things you can control (skeletal muscles)  Autonomic nervous system- Motor responses you can't consciously control (heartbeat)  ● Divisions of the PNS  

 Sensory Divisions of PNS  Sensory Division- This division gathers information from external and internal environment 

● There are two ways of gathering sensory information 1. General Senses   ● Specialized sensory receptors that we have throughout the body.   ■ Temp/pressure receptors on your skin  2. Special Senses  ● Specialized receptors in very specific organs in the body  ■ Vision, detecting light information. Requires specific receptors that are specialized to gather a certain kind of receptors.   Sensory receptor > action potential which travels through neuron > dorsal root of spinal nerve   ● Dorsal root of spinal nerve carry sensory information  ● Ventral root of spinal nerve carry motor information  ● These two roots come together to make a spinal nerve.  ● Spinal nerves in the body carry both sensory and motor info. 

 Motor Division of PNS  Somatic nervous system- CNS to skeletal muscles (which are voluntary controlled) ○ Single neuron system.   ● This division is located within the spinal cord. Axon exits the spinal cord and goes all the way to the muscle. Synapse with skeletal muscle- junction of a nerve cell with another cell ○ A synapse is a connection between two neurons or a connection between a neuron and a target tissue.  ○ Synapses are basically places where we're making decisions about our nervous system signals.   ● Do we want the signal to continue or should we block the signal at this stage? ○ In the case of the motor division, you can't stop a synapse, if the signal goes out, it will synapse with the skeletal muscle. 

Neuromuscular junction- a synapse between a neuron and skeletal muscle.   Signal start from CNS > skeletal muscle   Autonomic nervous system- from CNS to smooth muscle, cardiac muscle and certain glands. ○ Involuntary control.   ○ Two neuron system  ● First neuron goes from CNS to ganglion ● The first neuron joins with a second neuron called autonomic ganglion ● The second neuron goes from ganglion to effector  ● Two divisions of the Autonomic nervous system  ○ Sympathetic- prepares the body for physical activity (fight or flight response)  ● Increase heart rate/ breathing rate.  ● Is for when you go from a resting condition to a condition where you're moving   ○ Not always fight or flight. Ex. Getting up and climbing stairs.  ○ Parasympathetic- regulates resting or vegetative functions such as digesting food.  ● Active when you are resting.  ● Don't have them on in the same time in a target tissue  ● Could have sympathetic on in one target tissue and parasympathetic on in another target tissue as the same time.    Enteric Nervous system- plexuses within the wall of the digestive tract. Can control the digestive tract independently of the CNS, but still communicated with the CNS via the ANS (parasympathetic and sympathetic neurons contribute to the plexus) 

○ Our brain doesn’t need to always know what's happening in the digestive system for it to do it's job.   ○ So a plexuses associated with the digestive system all the process of digestion to go on without involving the CNS  ● Done by sensory and motor receptors  ● Sensory receptors inside the digestive tract monitor chemical environment and stretching of walls.   ○ Constantly monitoring what the contents in the tube are and how big/liquified they are.   ● Motor receptors contract smooth muscle and control secretions of GI organs and endocrine cells.     ...