chapter 4 - divisions of the nervous system

Question 1

what does the PNS consist of

Answer 1

• cranial nerves (12): arise from brain, most contain both motor and sensory nerves (mixed), some contain one or the other
• spinal nerves (31): arise from spinal chord, contain both motor and sensory nerves (mixed), joined to spinal chord via two routes
• > dorsal route: contains axons of sensory neurons that have cell bodies on a small swelling of dorsal root (dorsal root ganglion)
• > ventral route: contains axons of motor neurons that have cell bodies in grey matter of spinal chord

Question 2

what is the ANS (efferent division of PNS)

Answer 2

• function: controls bodies internal environment, involved in homeostatic mechanisms that keep internal environment constant, involuntary
• regulated by: groups of nerve in medulla oblongata, hypothalamus and the cerebral cortex
• regulates: heart rate, BP, body temp, digestion, release of energy, pupil diameter, airflow to lungs, defecation / urination

Question 3

autonomic vs somatic division (efferent division of PNS)

Answer 3

• effectors: A (heart muscle, involuntary muscle, glands) and S (skeletal; voluntary muscles)
• function: A (adjustment of internal environment, homeostasis) and S (response to external environment)
• pathway: A (2 nerve fibres from CNS to effector with a synapse in a ganglion) and S (1 nerve fibre from CNS to effector; no synapse / ganglion)
• neurotransmitter at effector: A (acetylcholine / noradrenaline) and S (acetylcholine)
• control: A (involuntary) and S (voluntary)
• nerves to target organ: A (two sets, sympathetic and parasympathetic) and S (one set)
• effect on target organ: A (excitation / inhibition) and S (excitation)

Question 4

sympathetic vs parasympathetic divisions (autonomic division of efferent division of PNS)

Answer 4

• heart: S (increases rate / strength of contraction) and PS (decreases rate and strength of contractions)
• lungs: S (dilates bronchioles) and PS (constricts bronchioles)
• stomach / intestine: S (decreases movement) and PS (increases movement)
• liver: S (increases breakdown of glycogen / releases glucose) and PS (increases uptake of glucose / synthesis of glycogen)
• iris of eye: S (dilates pupil) and PS (constricts pupil)
• sweat glands: S (increases sweat secretion) and PS (no effect)
• salivary glands: S (decreases secretion of saliva) and PS (increases secretion of saliva)
• skin BV: S (constricts V) and PS (little effect)
• skeletal muscle BV: S (dilates V) and PS (no effect)
• internal organs BV: S (constricts V except heart and lungs) and PS (no effect)
• urinary bladder: S (relaxes muscles) and PS (constricts muscles)
• adrenal medulla: S (stimulates hormone secretion) and PS (no effect)

Question 5

nervous system vs endocrine system

Answer 5

• nature of message: N (electrical impulses, neurotransmitters) and E (hormones)
• transport of message: N (along membrane of neurons) and E (bloodstream)
• cells affected: N (muscle / gland cells, other neurons) and E (all body cells)
• type of response: N (local and specific) and E (general and widespread)
• time taken: N (rapidly, ms) and E (slower, seconds to days)
• duration: N (brief, stops quickly once stimulus stops) and E (longer lasting, may continue long after stimulus has stopped)

Question 6

what are the divisions of the PNS

Answer 6

1. afferent (sensory) division: fibres carry impulses to CNS
2. 1 somatic sensory neurons: receptors in skin / around muscles + joints
3. 2 visceral sensory neurons: nerve cells in internal organs
4. efferent (motor) division: fibres that carry impulses from CNS to skeletal muscles
5. 1 somatic division: carries impulses from CNS to skeletal muscles
6. 2 autonomic division: carries impulses from CNS to heart muscle, involuntary muscles and glands
7. 2.1 sympathetic division: fight / flight effects
8. 2.2 parasympathetic division: relaxed effects (prepares body for rest)