Topic 6: Nervous System 4

Question 1

Autonomic Nervous System

Answer 1

• CNS -> smooth + cardiac muscle, glands
• 2 neurons to effector (preganglionic + postganglionic)
• any neuron can be distinguished by the type of nt released:
  1) Cholinergic = ACh
  2) Adrenergic = norepinephrine (NE)
• 2 divisions:
  1) Sympathetic Nervous System
  2) Parasympathetic Nervous System

Question 2

Sympathetic Nervous System

Answer 2

• Function = prepares body for activity
• Fight or flight response
• activated during exercise
• Diagram

Question 3

To stop chemical stimulation, need to remove nt (Sympathetic Nervous System)

Answer 3

1) ACh broken down by acetylcholinesterase (AChE) - on postsynaptic membrane (cell body/dendrites of postganglionic neutron, or effector cell)
2) NE broken down by MAO (monoamine oxidase) - in synaptic end bulb of neutron that released it

Question 4

Parasympathetic Nervous System

Answer 4

• Function: -rest + digest (Housekeeping)
• Most organs innervated by ANS have both SNS +PSNS - usually have opposite actions
• ANS regulates internal processes continuously and automatically
• eg. 1: Heart rate –> SNA excites, PSNS inhibits
• eg. 2: GI tract motility –> SNS inhibits, PSNS excites

Question 5

Higher Control of ANS

Answer 5

Cerebrum –> Hypothalamus –> Medulla Oblongata –> ANS –> SNS & PSNS

• Note: hypothesis. does not need cerebral input for its ANS functions, but emotions can cause autonomic effects
  e. g. blushing, fainting, cold sweat, high HR etc

Question 6

Effects of ANS

Answer 6

TABLE

Question 7

Somatic Nervous System

Answer 7

CNS(brain) (Upper motor neuron) –> CNS (spinal cord)(Lower motor neuron) –> E = skeletal muscle

Question 8

3 Types of Movement Somatic Nervous System

Answer 8

1) Reflexes
2) Voluntary
3) Rhythmic

Question 9

Reflexes

Answer 9

1) Spinal
- Least complex
- Require sensory input from (e.g. muscle spindles)
2) Postural - for balance and posture
- Require sensory input from e.g. proprioceptors (e.g. muscle spindles), eyes, inner ear

Question 10

Voluntary

Answer 10

• Most complex

- No external stimuli required (act of will)

Question 11

Rhythmic

Answer 11

• Walking, running etc,

- Combination of reflex + voluntary

Question 12

Level 1 of Motor Control

Answer 12

Planning
- Do you want to move? If yes, what movement needed? Which muscles need to contract?
- Plans sequence of muscle contractions
- Signals primary motor cortex
- Works with input from cerebellum
NOTE: Level 2 and 3: descending motor tracts to lower motor neurons

Question 13

Level 2 of Motor Control

Answer 13

• Signals directly to lower neurons (via corticospinal tract)
• For fine, skilled movements

Question 14

Level 3 of Motor Control

Answer 14

• Brain stem nuclei –> descending motor tracts to lower motor neurons (= indirect tracts)
• Receive input from cortex, basal nuclei, cerebellum
• Involved in co-ordination of large muscle groups for: - maintenance of posture - locomotion

Question 15

Level 4 of Motor Control

Answer 15

Spinal Cord

• Contains:
• Cell bodies of lower motor neurons
• Network of neurons (central pattern generates; CPGs) which set rhythmic , repeated movements (eg. walking, running)
• Require cortical signals to begin or stop movement

Question 16

Cerebellum

Answer 16

• Role in planning + initiating movement –> sends input to cortical areas
• Stores planned movement + compares actual to plan, using sensory input from e.g. proprioceptors - corrects if necessary
• Maintains balance, controls eye movements, has a role in maintaining muscle tone (= low level of contraction)
• Coordinates skilled voluntary muscle movements and timing of contractions involving more than 1 joint

Question 17

Basal Nuclei

Answer 17

• Aid in planning movement
• Suppress unwanted motions e.g. at rest
• Role in maintaining muscle tone

Question 18

Corticospinal (Direct) Pathway

Answer 18

• Cortex to skeletal muscle
• Parts:
  1) Upper motor neurons
  2) Lower motor neurone in spinal nerves

Question 19

Upper motor neurons (Corticospinal (Direct) Pathway)

Answer 19

• Cell bodies in primary motor cortex

- Axons down spinal nerves

Question 20

Lower Motor Neurons (Corticospinal (Direct) Pathway)

Answer 20

• Cell bodies in ventral horn of sp cord

- Axons exit via spinal nerves

Question 21

Destruction of Upper Motor Neruons

Answer 21

1) Spastic Paralysis - high muscle tone (no muscle atrophy)
2) Exaggerated reflexes e.g. patellar, achilles; babinski sign
- Plantar reflex - scratch sole of foot
- Normal = plantar flexion of toes (curl under)
- Babinski sign = extend big toe (indicates damage to upper motor neurons (except in babies where its normal - corticospinal tract not yet fully myelinated)

Question 22

Destruction of Lower Motor Neurons

Answer 22

• Get:
  1) Loss of reflex arc (no reflex)
  2) Flaccid paralysis ( lower tone, marked muscle atrophy)
• E.g. Polio (poliomyelitis) = virus destroys cell bodies in ventral horn of sp. cord

Question 23

Language

Answer 23

• Areas in left cortex of most people (equivalent ares on right side provide emotional components of language - e.g. tone of voice, gestures)

Question 24

Important Brain Regions (Language)

Answer 24

1) Cortex - for concepts and ides
2) Wernicke’s area, Broca’s area, basal nuclei
- Make up language implementation system
- Analyzes the incoming and produces outgoing word sounds and grammatical structures
3) Areas of the visual and auditory cortex
- Signals pass from language areas to premotor cortex to plan muscle contractions
- Primary motor cortex initiates planned contractions

Question 25

Damage to Wernicke’s Area

Answer 25

• Can’t understand spoken or written words –> can speak but words are meaningless or mixed up

Question 26

Damage to Broca’s

Answer 26

Understand words but difficult to speak or write sensibly