Autonomic Nervous System, Special Senses, and Endocrine System: Final Exam Review Notes

Chapter 14: Autonomic Nervous System & Higher Order Functions

Overview of the Autonomic Nervous System (ANS)

The Autonomic Nervous System (ANS) regulates involuntary physiological processes, including heart rate, blood pressure, respiration, digestion, and sexual arousal. It is divided into the sympathetic and parasympathetic divisions, which often have opposing effects.

• Sympathetic Division: Prepares the body for 'fight or flight' responses.

• Parasympathetic Division: Promotes 'rest and digest' activities.

• Dual Innervation: Most organs receive input from both divisions, allowing precise regulation.

Key Concepts

• Preganglionic vs. Postganglionic Neurons: Preganglionic neurons originate in the CNS and synapse with postganglionic neurons in autonomic ganglia.

• Neurotransmitters: Acetylcholine (ACh) is released by all preganglionic neurons; postganglionic neurons may release ACh or norepinephrine (NE), depending on the division.

• Sympathetic Pathways: Preganglionic neurons are short; postganglionic neurons are long.

• Parasympathetic Pathways: Preganglionic neurons are long; postganglionic neurons are short.

• Higher Order Functions: Include memory, learning, and consciousness, primarily managed by the cerebral cortex and limbic system.

Examples

• Sympathetic Activation: Increased heart rate, dilated pupils, decreased digestive activity.

• Parasympathetic Activation: Decreased heart rate, constricted pupils, increased digestive activity.

Additional info: The ANS also regulates reflexes such as baroreceptor and micturition reflexes.

Chapter 15: The Special Senses

Overview of Special Senses

The special senses include vision, hearing, equilibrium, taste, and smell. Each sense has specialized organs and receptors that convert environmental stimuli into neural signals.

• Vision: The eye contains photoreceptors (rods and cones) that detect light and color.

• Hearing & Equilibrium: The ear contains structures for detecting sound waves and maintaining balance.

• Taste (Gustation): Taste buds on the tongue detect chemicals in food.

• Smell (Olfaction): Olfactory receptors in the nasal cavity detect airborne chemicals.

Key Concepts

• Rods: Function in low light; contain rhodopsin.

• Cones: Responsible for color vision and visual acuity.

• Auditory Pathway: Sound waves travel through the external ear, vibrate the tympanic membrane, and are transmitted via ossicles to the cochlea.

• Equilibrium: The vestibular apparatus (utricle, saccule, semicircular canals) detects head position and movement.

Example Table: Comparison of Rods and Cones

Feature	Rods	Cones
Light Sensitivity	High (dim light)	Low (bright light)
Color Vision	No	Yes
Visual Acuity	Low	High
Pigment	Rhodopsin	Photopsins

Chapter 16: The Endocrine System

Overview of the Endocrine System

The endocrine system consists of glands that secrete hormones into the bloodstream to regulate body functions. Hormones act on target cells to influence metabolism, growth, reproduction, and homeostasis.

• Major Endocrine Glands: Pituitary, thyroid, parathyroid, adrenal, pancreas, pineal, thymus, gonads.

• Hormone Types: Peptide, steroid, and amino acid-derived hormones.

• Mechanisms of Action: Hormones bind to specific receptors on or in target cells, triggering signal transduction pathways.

Key Concepts

• Negative Feedback: Most hormone secretion is regulated by negative feedback loops.

• Second Messengers: Many hormones use cAMP or Ca2+ as intracellular messengers.

• Hypothalamic-Pituitary Axis: The hypothalamus controls the pituitary gland, which in turn regulates other endocrine glands.

Example Table: Major Endocrine Glands and Their Hormones

Gland	Hormone(s)	Main Function(s)
Pituitary (anterior)	GH, TSH, ACTH, FSH, LH, PRL	Growth, metabolism, stress, reproduction, lactation
Thyroid	T3, T4, Calcitonin	Metabolism, calcium regulation
Adrenal Cortex	Cortisol, Aldosterone	Stress response, sodium balance
Pancreas	Insulin, Glucagon	Blood glucose regulation
Ovaries/Testes	Estrogen, Progesterone, Testosterone	Reproduction

Example Equation: Negative Feedback Regulation

Hormone secretion is often regulated by negative feedback, which can be represented as:

$\text{Stimulus} \rightarrow \text{Endocrine Gland} \rightarrow \text{Hormone Release} \rightarrow \text{Target Organ Response} \rightarrow \text{Inhibition of Further Hormone Release}$

Additional info: Disorders of the endocrine system include diabetes mellitus (insulin deficiency or resistance), hyperthyroidism, and Addison's disease (adrenal insufficiency).