Week 4: Autonomic Pathways

Question 1

briefly explain the structural organization of the nervous system.

Answer 1

nervous system is divided into the central nervous system and the peripheral nervous system.
the peripheral nervous system is divided into the sensory afferent division and the motor efferent division. the motor efferent division is divided into somatic nervous system and autonomic nervous system. the autonomic nervous system is further divided into the sympathetic and parasympathetic nervous system.

Question 2

in somatic nervous system, how does the lower motor neuron work ?

Answer 2

1. the upper motor neuron originates in the primary motor cortex: precentral gyrus of the frontal lobe.
2. the axon of the upper motor neuron travels down into the brainstem and through the spinal cord.
3. the upper motor neuron synapses with the lower motor neuron in the anterior gray horn of the spinal cord.
4. lower motor neuron: located in the anterior gray horn of the spinal cord or in the cranial nerve nuclei.
5. after synapsing, the lower motor neuron axon exits the spinal cord via the anterior root and travels to the skeletal muscle.
6. the axon of the lower motor nerve reaches the muscle where it releases acetylcholine which binds to muscle fibers causing the muscle to contract.

Question 3

what is the location of the neuronal cell body, axons, and effector in the case of somatic ? what is the neurotransmitter going to be ?

Answer 3

neuronal cell body: central nervous system
axons: peripheral nervous system
effector: skeletal muscles
neurotransmitter is always acetylcholine: stimulates muscle contractions.

Question 4

in autonomic pathway, what is the first and second neuron called ?

Answer 4

first neuron: preganglionic neuron
second neuron: postganglionic neuron

Question 5

sympathetic nervous system pathway ?

Answer 5

1. the cell body of the preganglionic neuron is located in the central nervous system specifically the lateral gray horn of the spinal cord. the myelinated axon of this neuron extends out into the peripheral nervous system.
2. in the PNS, the axon of the preganglionic neuron will synapse with the postganglionic neuron. the neurotransmitter acetylcholine is released when synapsed.
3. the postganglionic neuron has its cell body in the autonomic ganglion. its axon is unmyelinated and projects to the effector tissue such as: glands, cardiac muscle, and smooth muscle.
4. the postganglionic neuron releases norepinephrine which triggers a response.

Question 6

what is the neurotransmitter norepinephrine responsible for ?

Answer 6

this neurotransmitter/hormone plays an important role in the body’s fight or flight response.
- increase heart rate, vasoconstriction, etc.

Question 7

parasympathetic nervous system pathway ?

Answer 7

1. the cell body of the preganglionic neuron is located in the central nervous system specifically the sacral region of the spinal cord. the myelinated axon of this neuron extends out into the peripheral nervous system.
2. in the PNS, the axon of the preganglionic neuron will synapse with the postganglionic neuron. the neurotransmitter acetylcholine is released when synapsed.
3. the postganglionic neuron has its cell body in the autonomic ganglion. its axon is unmyelinated and projects to the effector tissue such as: glands, cardiac muscle, and smooth muscle.
4. the postganglionic neuron releases acetylcholine which triggers a response.

Question 8

what is the neurotransmitter acetylcholine responsible for ?

Answer 8

in the somatic system, acetylcholine is involved in muscle contraction is somatic system.
in the autonomic system, it is involved in parasympathetic functions like slowing the heart rate and promoting digestion.

Question 9

differences between the sympathetic pathway and parasympathetic pathway ?

Answer 9

what is being released at the effector:
in parasympathetic, it is acetylcholine and in sympathetic, it is norepinephrine.
location of the autonomic ganglion:
in sympathetic, it is close to cns and far from effector tissue. in parasympathetic, it is far from cns and close to effector tissue.
symapethic: have the ability to have hormonal responses. still have a

Question 10

another function of sympathetic nervous system that parasympathetic can’t do.

Answer 10

sympathetic: have the ability to have systemic hormonal responses. still have a preganglionic neuron in the lateral gray horn. axon projects out through anterior root of spinal nerve, travels into the adrenal medulla, the acetylcholine is released and target the chromaffin cells. these chromaffin cells release epinephrine as a hormone into the blood.
- epinephrine aka adrenaline released into blood has a prolonged and widespread effect throughout the body.