Motor control, relexes, & senses

Question 1

Efferent Nervous System
Motor control

Answer 1

NS uses many sensory inputs to plan motor actions
Processed consciously in the cerebral cortex
Processed unconsciously in other parts of CNS
A few senses are especially important for unconscious processing

Question 2

Somatic senses

Answer 2

Efferent senses of the body
1. Proprioception: sense of position of limbs
2. Vestibular sense: sense of balance

Question 3

Proprioception

Answer 3

sense of position of limbs
- Muscle spindles - in skeletal muscle organs detect stretch = length of muscle
- Gogi tendon organs - in tendons right next to muscle detect tension = force on muscle

Question 4

Vestibular sense

Answer 4

Sense of balance
- In inner ear
- Detects position and motion of head

Question 5

Premotor Complex

Answer 5

• Plans complex motions involving multiple muscle groups
• Receives signals from sensory cortices + association areas

Question 6

Primary motor complex

Answer 6

• Directly controls somatic motor neurons
• Has a homunculus = map of the body
• Receives signals from premotor cortex

Question 7

Cerebellum

Answer 7

Helps generate smooth + coordinated motions
- Compares motor complex plan to what is actually going on
- Gets signals from the motor cortex
– Somatic senses - especially proprioception + vestibular sense)
- Sends signals back to the motor cortex

Question 8

Basal ganglia

Answer 8

Helps coordinate motor actions by receiving signals from all parts of the cortex, then sends signals back to the premotor complex.
At default, it suppresses cortex from generating motions
Most release suppression to move.

Question 9

Giant Pyramidal Neurons

Answer 9

• Cells bodies are in the primary motor complex
• Axons goe down the spinal cord
• Synapse on somatic motor neurons in the spinal cord
• Contains Pyramidal Tracts

Question 10

Pyramidal Tracts

Answer 10

White matter tracks that pyramidal axons travel down
Ventral
Direct = go directly from cortext to motor neurons

Question 11

Structures of Motor Control
in the Efferent Nervous System

Answer 11

• Premotor cortex
• Primay motor cortex
• Cerebellum
• Basal Ganglia
• Giant Pyramidal Neurons
• Pyramidal tracks
• Motor neurons that leave CNS & make muscles contract

Question 12

Reflex

Definition + Types

Answer 12

= An automatic (unconscious) response to a stimuli
- Faster than conscious thought
- Conscious thought can overcome reflexes
Reflex Types:
- Autonomic
- Somatic
- Pollysynaptic
- Monosynaptic
- Short
- Long

Question 13

Reflex Arc

Answer 13

Series of neurons that a reflex passes through
Receptor = detects the stimulus
1. Signals the Afferent neuron = carries the signal from receptor to integration center
2. Integrating center = processes information about the stimulus + makes decisions
3. An efferent neuron = carries the signal from integrating center to effector
4. Effector gets signal from efferent neuron + does something (ex: muscle contraction)

Question 14

Autonomic Reflex

Answer 14

= efferent neurons are autonomic + effector for smooth muscle, cardiac muscle, glands or adipose

Question 15

Somatic Reflex

Answer 15

= efferent neurons are somatic motor neurons + the effector is always skeletal muscle

Question 16

Short Reflex

Answer 16

Integrating center in PNS
- Only autonomic or visceral

Question 17

Long Reflex

Answer 17

Integrating center in CNS
- Autonomic or somatic
- Somatic have to be long because the cell bodies are in the CNS

Question 18

Monosynaptic Reflex

Answer 18

= reflex with only 1 synapse
- Afferent neuron synapses directly on an efferent neuron
- The integration center is synapse + decision by efferent neuron to have AP

Question 19

Polysynaptic Reflex

Answer 19

= reflex with more than 1 synapse, have at least 1 interneuron between the afferent + efferent neuron - that creates multiple synapses

Question 20

What reflexes do the brain stem control?

Answer 20

Complex somatic reflexes:
- Breathing
- Maintaining balance + posture
- Responding to visual + auditory stimuli
- All polysynaptic

Question 21

Indirect pathways

Answer 21

= white matter tracts in the spinal cord
- Neurons with cell bodies in the brain stem
- Axons travel down the spinal cord in indirect pathways
- Neurons synapse on interneurons in the grey matter of the spinal cord
- Interneurons synapse on somatic motor neurons

Question 22

Spinal Reflexes

Definition + Types

Answer 22

• Somatic reflexed
• Integration center in the spinal cord
• Monosynaptic or polysynaptic
• Synapses in the gray matter of the spinal cord
  Types of spinal reflexes:
• Stretch reflex
• Tendon reflex
• Flexor reflex
• Crossed-extensor reflex

Question 23

Stretch reflex

Answer 23

When muscle is stretched, it contracts in response (as a reflex)
Initiate the reflex by hitting a tendon:
1. Muscle spindle in muscle detects stretch
2. Sends signal to spinal cord on an afferent motor neuron
3. In spinal cord afferent neurons synapse on the monosynaptic motor neuron for the same muscle
4. Efferent motor neuron carries signals to muscle that was stretched + signals the muscle
5. Muscle contracts

Question 24

Reciprocal Inhibition

Answer 24

The antagonist to the stretch reflex that makes the other muscles relax for the flex to occur.
Polly synaptic
Afferent neuron synapses on an interneuron
The interneuron inhibits the motor neuron + on the antagonistic muscle