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CNS and PNS

CNS - brain + spinal cord, body’s command center for processing things, memory, and regulation

PNS - cranial nerves + spinal nerves + peripheral sensory receptors, connect CNS to limbs, organs and skin to relay info

PNS subgroups

-filled with afferent and efferent nerves

-efferent nerves have somatic (voluntary skeletal muscles) and autonomic (involuntary cardiac, smooth, glands)

Somatic NS:

voluntary skeletal muscle, single motor neuron → fast/precise actions (sprint, jump, kick).

Autonomic NS (involuntary):

-Sympathetic (fight/flight): ↑ HR & contractility,

bronchodilation, fuel release, vasoconstriction in

non-working tissues.

-Parasympathetic (rest/digest): ↓ HR, recovery,

GI activity

What is the pathway between the CNS and PNS

Stimulus → Receptor → Afferent → CNS

→ Efferent → Effector → Response.

Is shivering autonomic or somatic?

Its somatic skeletal muscle contractions

Intrinsic activity of cardiac control during exercise

SA node sets rhythm.

extrinsic activity of cardiac control during exercise

-part of the autonomic nervous system

-Sympathetic (β₁): ↑ HR & contractility → ↑ SV→ ↑ CO.

-Parasympathetic (vagus): ↓ HR (dominant at rest/early recovery).

Baroreceptor reflex in cardiac control during exercise

-Carotid sinus, aortic arch

-↑ BP → ↑ firing → ↑ vagal, ↓ sympathetic → HR falls (opposite if ↓ BP).

medulla/pons role in breathing control during activity

-set rhythm

-higher centres drive exercise onset

central chemoreceptors role in breathing control during activity

• ↑CO₂ / ↓pH → ↑ ventilation

peripheral chemoreceptors role in breathing control during activity

-respond to ↓O₂

-↑CO₂, ↓pH

proprioceptors role in breathing control during activity

rapid rise at movement start.

Proprioceptors

-spindles, GTO

-sense position/stretch/tension

-posture, coordination, reflexes.

Baroreceptors

-Carotid sinus, aortic arch

-sense BP/stretch

-adjust HR & vessels

Chemoreceptors

-carotid/aortic, medulla

-sense CO₂, O₂, pH → adjust ventilation

How hormone control body systems

-circulate in blood, act only on target cells with receptors

-coordinate with nervous system to regulate fuel, fluids, stress, growth, reproduction

how does negative feedback work

-rise → inhibit

-fall → stimulate.

CNS and PNS

cns - brain and spinal cord,

pns - Cranial nerves spinal nerves peripheral sensory receptors,