Anatomy Lab 11/9

With the voluntary nervous system it takes ___ neuron to get a

1 neuron to get a nerve impulse from the CNS to the muscle

The flexor reflex

1. a noxious stimulus activates the afferent sensory fiber to the spinal cord 2. multiple interneurons (polysnaptic) receive the electrical current 3. on the ipsilateral side the interneurons cause an: - EPSP in the efferent motor neurons to the flexor muscles (biceps) - IPSP in the efferent motor neurons to the extensor muscles (triceps) 4. The result is the biceps contract, the triceps relax and the arm flexes away rom the potential harmful stimulus

The mechanism of tendon reflex

1. imagine fast contraction of the quadriceps muscles 2. this will actuate the tendon organ receptors in the quadriceps tendon 3. sensory impulses will be transmitted to the spinal cord and innervate 2 interneurons 4. one interneuron is excitatory and one in inhibitory 5. the inhibitory interneuron will fire an IPSP to the motor neuron which supplies the quadriceps muscle (so they will relax) 6. the excitatory interneuron will fire an EPSP to the motor neuron which supplies the hamstring muscles (so they will contract)

The mechanism of the stretch reflex

1. imagine fast stretch of the quadriceps muscles 2. this will activate the muscle spindles in the quadriceps femurs 3. sensory impulses will be transmitted to the signal cord and innervated 2 interneurson 4. one interneuron is excitatory and one in inhibitory 5. the excitatory interneuron will fire an EPSP to the motor neuron which supplies the quadriceps muscles (so they will contract) 6. the inhibitory interneuron will fire an IPSP to the motor neuron which supplies the hamstring muscles (so they will relax)

The crossed-extensory reflex

1. on the contralateral side the interneurons cause an: - IPSP in the efferent motor neurons to the flexor muscles (biceps) - EPSP in the efferent motor neurons to the extensor muscles (triceps) 2. the result is the bicep relax, the triceps contract and the arm pushes away from the potential harmful stimulus

The tendon reflex

1. quadriceps strongly contracts. tendon organs are activated 2. afferent fibers synapse with interneurons in the spinal cord 3a. efferent impulses to muscle with stretched tendon are damped. Muscle relaxes, reducing tension 3b. efferent impulses to antagonist muscle cause it to contract

What are the components of all hymn reflex arcs?

1. receptor 2. sensory neuron 3. integration center (one or more neurons in the spinal cord) 4. motor neuron 5. effector (muscle fiber or gland)

The patellar knee-jerk reflex - an example of a stretch reflex

1. tapping the patellar ligament stretches the quadriceps and excites its muscle spindles 2. afferent imposes travel to the spinal cord, where synapses occur with motor neurons and interneurons 3a. the motor neurons send activating impulses to the quadriceps causing it to contract, extending the knee. 3b. the interneurons make inhibitory synapses with ventral horn neurons that prevent the antagonist muscles (hamstrings) from resisting the contraction of the quadriceps

with the ANS is take __ neurons to get a

2 neurons to get a nerve impulse from the CNS to the organ.

The voluntary nervous system is the part of the

PNS that regulates body activities under conscious control

site of stimulus:

a noxious stimulus causes a flexor reflex on the same side, withdrawing that limb

1. when stretch activates muscle spindles, the associated sensory neurons transmit

afferent impulses at higher frequency to the spinal cord

The knee jerk reflex: - it keeps us standing upright. Your knees begin to bend (buckle), your quadriceps muscles will stretch and this will send

afferent impulses to the spinal cord.

A stretch reflex activates the agonist muscle and inhibits the

antagonist muscles

The knee jerk reflex: the sensory nerves from the muscle spindles are activated due to the stretch quads, and they communicate directly with motor neurons in the spinal cord. - the motor neurons will cause the quadriceps muscle to contract, and the

antagonistic muscles ( the hamstrings - semitendinosus, semimembranosus and biceps femoris) to relax, maintaining their normal length, this will stop your knees from bending and keep your body upright (imagine returning to the upright position in slow motion)

Site of reciprocal activation:

at the same time, the extensor muscles on the opposite side are activated

mediated through the autonomic nervous system =

autonomic (visceral)

Reflexes are either

autonomic or somatic

The cell body of the motor neuron is located in the

brain or spinal cord

the cell body of the pregananglionic neuron is in the

brain or spinal cord

The autonomic nervous system serves teh

cardiac muscles smooth muscles internal glands

3a. Efferent impulses of alpha motor neurons cause the stretched muscle to

contract, which resists or reverses the stretch

The stretch reflex result is a

contraction of the agonist and relaxation of the antagonist muscle

The flexor reflex is offed accompanied by the

crossed extensor reflex

autonomic (visceral) regulates

digestion, elimination, blood pressure, salivation, sweating

The stretch reflex is an

excitatory monosynaptic reflex arc.

the cell body of the ganglionic neuron is located in a

ganglion outside the CNS

monosynaptic

have one sensory and one motor neuron only (e.g. the knee-jerk reflex)

The tendon reflex is an

inhibitory polysynaptic reflex arc

The job of the stretch reflexes is to

make sure the muscles stay at this length to maintain our normal posture.

most reflexes are polysynaptic but some are

monosynaptic

What is the 1 neuron it takes to get a nerve impulse from the CNS to the muscle called?

motor neuron

Reflexes occur in reflex arcs -

neural pathways that mediate a reflex action

flexor reflex occurs when a

noxious (potentially tissue damaging) stimulus causes automatic withdrawal of a body part.

crossed-extensor reflex which affects the

opposing limb.

The tendon reflex - a response that is

opposite to the stretch reflex

the parasympathetic division of ANS

preganglionic neurons are located in the cranial area- forming cranial nerves III, VII, IX, X and the sacral areas, S2-S4. Both synapse with the ganglionic neuron which then sends a very short axon to hteo rgan it serves.

The sympathetic Division of ANS

preganglionic neurons are located in the thoracolumbar area with the cell bodies located in the lateral horns. From T1 to L2. pregnaglionic neurons leave the spinal cord ---> spinal nerve ------> ventral rams ------> white rams comminucans ------> sympathetic trunk ganglion --->---->----> spinal nerve

Reflexes are

rapid, involuntary motor responses to stimuli

3b. Efferent impulses of alpha motor neurons to antagonist muscles are

reduced (reciprocal inhibition)

The autonomic (involuntary) Nervous System is part of the PNS that

regulates body activities not under conscious control

The tendon reflex- result is a

relaxation of the agonist and contractions of the antagonist muscle

somatic activates

skeletal muscle

the voluntary nervous system serves the

skeletal muscles

autonomic (visceral) activates

smooth muscle - cardiac muscle - glands

mediated through the somatic nervous system

somatic

The stretch reflex response is to a

stretch of the agonist mucle

The knee jerk reflex: - afferent impulses were sent to the spinal cord. If the quad continued to stretch( imagine squatting in slow motion), your legs would giveaway and you'd fall on your rear end. However, the sensory nerves from the muscle spindles, are activated due to the

stretching quads, and they communicate directly with motor neurons in the spinal cord

The tendon reflex - response is to a

strong contraction of the agonist muscle

2. the sensory neurons synapse directly with alpha motor neuron, which excite extrafusal fibers of the stretched muscle. Sensory fibers also

synapse with interneurons that inhibit motor neurons controlling antagonistic muscles

what is the pregananglionic neuron?

the first neuron it takes to get a nerve impulse from the CNS to the organ.

what is the ganglionic neuron?

the second neuron it takes to get a nerve impulse from the CNS to the organ

Example f tendon reflex When a soccer player kids a ball there is a very rapid contraction of the quadriceps muscles . This activates the tendon organs in the quadriceps tendon. The resultant activity

through the polysnaptic reflex arc is what relaxes the quads and contracts the hamstrings so his leg will not continue with an upward trajectory but will return back to the ground and he won't fall over.

constant sensory information from our skeletal muscles to the brain sets the normal length of a muscle; so the brain knows

what the non-contracted, non-stretch (or relaxed) length is for every muscle in the body.