4.2 peripheral nervous system

what is the function PNS

takes messages from receptors to the central nervous system and from the central nervous system to muscles/glands.

what is the PNS composed of

-nerve fibres that carry info to and from the CNS

-ganglia (groups of nerve cell bodies), which lie outside the brain and spinal cord

what are the types of nerves

cranial and spinal nerves

key information about cranial nerves?

-12 pairs of nerves

-mixed nerves (contain fibres that carry impulses into the brain, and away from the brain)

-cranial nerves= mostly mixed, very few are only motor/sensory

differentiate between sensory and motor fibres:

sensory fibres= carry impulses to the CNS

motor fibres= carry impulses away from the CNS

describe the layout of spinal nerves in the spinal cord

the ventral root contains the axon of a motor neuron, and their cell body in the grey matter of the spinal cord. dorsal root contains the axon of sensory neurons, their cell body found in the dorsal root ganglion (small swelling).

how is the peripheral nervous system separated?

separated into the afferent and efferent division

what does the afferent division do?

has fibres that carry impulses to the CNS by sensory neurons from receptors in the skin and around the muscles and joints.

how can sensory neurons further be divided?

somatic sensory neurons= bring impulses from the skin and muscles

visceral sensory neurons= bring impulses from the internal organs

what does the efferent division do ?

has fibres that carry impulses away from the CNS (by motor neurons)

How is the efferent division further divided?

divided into the somatic division=(takes impulses from the CNS to the skeletal muscles)

also divided into the autonomic division=(carries impulses from the CNS to the heart muscle, involuntary muscles and glands.)

how is the autonomic division further divided?

divides into the sympathetic division and parasympathetic division.

what is the function of the ANS

controls the body’s internal environment and is involved in keeping it constant, operating unconsciously

how is the ANS regulated

groups of nerve cells in the medulla oblongata, hypothalamus and cerebral cortex

what are some bodily functions regulated by the ANS

heart rate, blood pressure, body temp, urination, air flow to lungs, digestion, pupil diameter

contrast between autonomic and somatic division

• ANS maintains homeostasis, SNS responds to external stimuli

• ANS=trasnmitted by 2 nerve fibres from the CNS with a synapse in a ganglion, SNS transmitted by 1 nerve fibre from the CNS without synapse and no ganglion

• ANS = involuntary, SNS = voluntary

• ANS targets heart muscle, involuntary muscles and glands. SNS targets skeletal muscles.

differentiate between the sympathetic and parasympathetic system

sympathetic= produces flight or fight response, enables body to response to stress.

parasympathetic= rest and digest, maintains homeostasis