Nervous system ppt/question, Schemes and Mind Maps of Law

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AUTONOMIC NERVOUS

SYSTEM_

Dr Reem Abraham

1. Apply the role of the hypothalamus and brainstem to the autonomic (autonomous) nervous system regulation mechanism of maintaining blood pressure homeostasis during exercise and exertion.
2. Describe and understand the effects of autonomic nervous system activity on organs and organ systems; examples: control of heart rate, liver cell metabolism

LEARNING OBJECTIVES

At the end of this lecture, students should be able to:

Autonomic control areas

in the brain stem and

hypothalamus

Levels of ANS Control

• (^) ANS functions are controlled by centers located in the spinal cord, brain stem, hypothalamus, cerebral cortex
• (^) Autonomic centers (BP, respiratory center etc) in the reticular formation of brain stem are controlled by hypothalamus
• (^) Visceral reflexes convey sensory signals from visceral organs to autonomic ganglia, brain stem, hypothalamus
• (^) Efferent autonomic signals are conveyed via sympathetic and parasympathetic nervous systems to homeosta sis

Medulla **NTS has two functional divisions:

1. Rostral part - taste
2. Caudal part - visceral sensory input → visceral motor output Visceral afferent information is relayed to the medulla, specifically to the caudal solitary nucleus (a.k.a. nucleus tractus solitarius/NTS) The NTS integrates and processes the visceral sensory information:**

• (^) mediates autonomic reflexes locally for immediate response
• (^) relays input to higher centers such as the hypothalamus for prolonged/delayed responses Nucleus Tractus Solitarius (NTS) in medulla: Visceral sensory integration center

Adrenal medulla

• (^) A specialized ganglion in the sympathetic

division of the autonomic nervous

system.

• (^) Cell bodies of its preganglionic neurons

are located in the thoracic spinal cord.

• (^) Axons of these preganglionic neurons

travel in the greater splanchnic nerve to

the adrenal medulla

Preganglionic neuron

Muscles of the iris

• (^) Two muscles: the sphincter pupillae and the dilator pupillae, regulating the amount of light entering the eye. The sphincter pupillae (inner aspect):
• Concentrically arranged muscle fibers
• Receives parasympathetic innervation
• Contraction results in pupillary constriction The dilator pupillae (outer aspect):
• Radial muscle fibers; radially arranged
• Receives sympathetic innervation
• Contraction results in pupillary dilation ANS and CONTROL OF PUPIL SIZE

• Radiating muscle fibers
• Sympathetic stimulation → dilation → mydriasis
• Circular muscle fibers
• Parasympathetic stimulation → contraction→ miosis ANS and CONTROL OF PUPIL SIZE

2. Pupillary constrictor (sphincter) muscle.

• (^) Controlled by parasympathetic innervation through muscarinic receptors.
• Activation of these muscarinic receptors ( M 3 ) causes
• (^) constriction of the sphincter muscle, which causes constriction of the pupil, or miosis
• (^) ciliary muscle contraction (accommodation) ANS and CONTROL OF PUPIL SIZE

P Metabolic effects of sympathetic stimulation Release of glucose from the liver Increase in blood glucose concentration Increase in glycogenolysis in both liver and skeletal muscle Increase in basal metabolic rate

ANS and exercise

• (^) During exercise: High metabolic demand by the active skeletal muscles
• (^) ANS ensures this by regulating sympathetic and parasympathetic activity
• (^) Activation/stimulation of sympathetic nervous system in exercise HEART RESP SYSTEM GIT SWEATING

Regulation of blood pressure during exercise Hypothala mus Sensory input Central command: cerebral cortex, limbic system Catecholamin es Cutaneous vasodilation Heat loss Sympathetic output Heart rate, SV CO SBP BP Blood vessels VASODILATION in skeletal muscle blood vessels (accumulation of local metabolites) Medulla NTS, VMC, CIC

Practice question

• (^) Activation of which of the following receptors increases total peripheral resistance (TPR)? a. α 1 Receptor b. β 1 Receptor c. β 2 Receptor d. M 3 receptors e. Nicotinic receptors