Nerves

Question 1

What do dendrites do?

Answer 1

They recieve signals from other neurons.

Question 2

What do axons do?

Answer 2

Carry signal in form of nerve impulses.

Question 3

What is a synapse?

Answer 3

The site of communication between 2 neurons.

Question 4

What is happening at the synapse?

Answer 4

1. Ariival of action potential at axon terminal of pre-synaptic neuron causes release of neurotransmitter.
2. Neurotransmitter diffuses across cleft and activates receptors on dendrite of post synaptic neuron.
3. Depending on the type of receptor activated, the post-synaptic neuron is excited or inhibited.

Question 5

What is a neuro-effector junction?

Answer 5

Site of communication between axon terminals of a motor neuron and its target tissue.

Question 6

What determines a neurons shape?

Answer 6

The number of synaptic inputs it receives and the number of targets it reaches.

Question 7

What are nociceptors?

Answer 7

Branched endings of somatic afferent neurons that are activated by stimuli that cause tissue damage.

Question 8

Where is the cell body of a general somatic afferent (GSA) neuron?

Answer 8

Dorsal root ganglia

Question 9

What is the shape of a neuron called?

Answer 9

Pseudounipolar; Cranial nerves are also similar to this.

Question 10

Describe the connections made by nociceptor GSAs

Answer 10

Once in the posterior horn of the spinal cord, it branches and synapses with Interneurons; Some are excitatory, others are inhibitory

Question 11

Where is the final destination of signals from nociceptors?

Answer 11

The brain or in some cases the spinal cord.

Question 12

Describe the morphology of a GSE neuron.

Answer 12

Neuron dendrites and cell body are in the Ventral horn of the spinal cord. Axon reaches from the spinal cord to the muscle it innervates. Has a multipolar shape.

Question 13

Summarize the nociceptor reflex.

Answer 13

Stimulus, Activation of nerve endings, Action potential of GSA, Action potential in CNS (Pain sensation), Activation of motor neuron in flexor muscles, Inhibition of extensor muscles, Withdrawal from stimulus.

Question 14

Describe the contents of a neuron cell body.

Answer 14

Large nucleus, golgi, and SER. Prominent aggreagates of RER on ribosomes. Lots of mitochondria

Question 15

What the role of the cytoskeleton?

Answer 15

It maintains the complex shape of the cell body, and provides the mechanism for intracellular transport.

Question 16

Describe the surroundings of a dendrite.

Answer 16

Covered with synapses from other neurons; Has small projections along dendrites that provide additional areas for synaptic contact.

Question 17

What the relationship between the number of dendrites/synapses and the use of the neuron?

Answer 17

The is a direct relationship.

Question 18

What is the axon hillock? Initial Segment?

Answer 18

The region where an axon joins the cell body; The initial segment is the beginning of an axon in which action potential are formed.

Question 19

Why is axon diameter important?

Answer 19

Diameter affects conduction velocity; Its a direct relationship.

Question 20

Where are the widest neruons? Narrowest?

Answer 20

Widest neurons are found in GSEs to skeletal muscles and GSAs mediating touch and muscle stretch/tension. Narrowest neurons are found in mediation of slow pain and post ganglionic sympathetic efferent neurons.

Question 21

What the drawback of a large neuron?

Answer 21

Takes up more room within a nerve; More susceptible to nerve block by compression.

Question 22

What is a myelin sheath?

Answer 22

Formed when a glia cell (Schwann cell in the PNS or oligodendrocytein the CNS) wraps its CM numberous times around an axon.

Question 23

What are nodes of ranvier?

Answer 23

Gaps in myelin sheath.

Question 24

What is the function of the myelin sheath?

Answer 24

To provide protection and electrical insulation around an axon.

Question 25

Describe Saltatory conduction.

Answer 25

Action potentials jumping from node to node; A result of myelination. This process increases the velocity of the action potential.