Anatomy & Physiology: Nervous, Sensory, and Endocrine Systems Study Guide

Chapter 7: Nervous System

Overview of the Nervous System

The nervous system is responsible for coordinating and regulating bodily functions through electrical and chemical signals. It is divided into the Central Nervous System (CNS) and Peripheral Nervous System (PNS), each with distinct roles.

• Primary Functions: Sensory input, integration, motor output.

• CNS: Composed of the brain and spinal cord; processes information and initiates responses.

• PNS: Consists of nerves and ganglia outside the CNS; connects the CNS to limbs and organs.

• Sensory (afferent) division: Transmits sensory information to the CNS.

• Motor (efferent) division: Carries commands from the CNS to effectors (muscles/glands).

Functional Subdivisions

• Somatic Nervous System: Controls voluntary movements via skeletal muscles.

• Autonomic Nervous System (ANS): Regulates involuntary functions (e.g., heart rate, digestion).

• Sympathetic Division: Mobilizes body systems during activity ("fight or flight").

• Parasympathetic Division: Conserves energy and promotes "rest and digest" functions.

Neuroglia and Supporting Cells

Neuroglia are non-neuronal cells that provide support, protection, and nutrition to neurons.

• Astrocytes: Maintain the blood-brain barrier, provide nutrients, and repair tissue.

• Microglia: Act as immune cells in the CNS.

• Ependymal Cells: Line ventricles and produce cerebrospinal fluid (CSF).

• Oligodendrocytes: Form myelin sheaths in the CNS.

• Schwann Cells: Form myelin sheaths in the PNS.

• Satellite Cells: Support neurons in the PNS.

Structure and Function of Neurons

Neurons are specialized cells for transmitting electrical impulses.

• Cell Body (Soma): Contains the nucleus and organelles.

• Dendrites: Receive signals from other neurons.

• Axon: Conducts impulses away from the cell body.

• Axon Hillock: Initiates action potentials.

• Nodes of Ranvier: Gaps in myelin sheath that facilitate rapid signal transmission.

• Myelin Sheath: Insulates axons, increasing conduction speed.

Types of Nerve Fibers

• Nerves: Bundles of axons in the PNS.

• Tracts: Bundles of axons in the CNS.

• Gray Matter: Contains neuron cell bodies.

• White Matter: Contains myelinated axons.

Neuron Classification

• Motor Neurons: Carry impulses from CNS to effectors.

• Sensory Neurons: Transmit impulses from receptors to CNS.

• Interneurons: Connect neurons within the CNS.

Types of Sensory Receptors

• Free Nerve Endings: Pain receptors.

• Meissner's Corpuscle: Touch receptors.

• Proprioceptors: Detect movement, posture, and muscle tone.

Graded and Action Potentials

• Graded Potential: Local change in membrane potential; varies in size.

• Action Potential: All-or-nothing electrical impulse; travels long distances.

• Threshold: Minimum stimulus required to trigger an action potential.

• Depolarization: Membrane potential becomes less negative.

• Repolarization: Membrane potential returns to resting state.

• Hyperpolarization: Membrane potential becomes more negative than resting.

Equation:

$V = IR$ (Ohm's Law, where V = voltage, I = current, R = resistance)

Synapses and Reflexes

• Synapse: Junction between two neurons; includes presynaptic neuron, synaptic cleft, and postsynaptic neuron.

• Neurotransmitters: Chemical messengers released at synapses.

• Reflex: Rapid, involuntary response to a stimulus.

• Reflex Arc: Pathway involving sensory neuron, interneuron, and motor neuron.

Brain and Meninges

Major Regions of the Brain

• Cerebral Hemispheres: Largest part; responsible for higher functions.

• Diencephalon: Includes thalamus, hypothalamus, epithalamus.

• Brain Stem: Midbrain, pons, medulla oblongata; controls vital functions.

• Cerebellum: Coordinates movement and balance.

Cerebral Cortex Functions

• Primary Somatic Sensory Area: Processes sensory input.

• Primary Motor Area: Controls voluntary movements.

• Broca's Area: Speech production.

• Anterior Association Area: Complex cognitive functions.

• Posterior Association Area: Integrates sensory information.

Meninges and Cerebrospinal Fluid

• Dura Mater: Tough outer layer.

• Arachnoid Mater: Middle layer; web-like.

• Pia Mater: Delicate inner layer.

• Cerebrospinal Fluid (CSF): Cushions and protects the brain and spinal cord.

Cranial and Spinal Nerves

• Cranial Nerves: 12 pairs; serve head and neck.

• Spinal Nerves: 31 pairs; serve the rest of the body.

Chapter 8: Sensory System

External Anatomy of the Eye

• Iris: Controls pupil size.

• Sclera: White, protective outer layer.

• Pupil: Opening for light entry.

• Cornea: Transparent front part; refracts light.

• Eyelids, Eyelashes, Lacrimal Apparatus: Protect and lubricate the eye.

• Conjunctiva: Mucous membrane covering the eye.

Internal Anatomy of the Eye

• Vitreous Humor: Gel filling the eye.

• Aqueous Humor: Fluid in anterior chamber.

• Lens: Focuses light.

• Retina: Contains photoreceptors (rods and cones).

• Optic Nerve: Transmits visual information to the brain.

• Rods: Detect dim light; black and white vision.

• Cones: Detect color; require bright light.

Photoreceptors and Vision

• Rods: More numerous; sensitive to low light.

• Cones: Concentrated in the fovea; responsible for color vision.

Eye Reflexes and Accommodation

• Photopupillary Reflex: Pupil constricts in response to bright light.

• Accommodation: Lens changes shape to focus on near or distant objects.

External and Internal Anatomy of the Ear

• Auricle: External ear structure.

• External Acoustic Meatus: Ear canal.

• Tympanic Membrane: Eardrum.

• Auditory Ossicles: Malleus, incus, stapes; transmit sound vibrations.

• Cochlea: Spiral organ for hearing.

• Semicircular Canals: Balance and equilibrium.

Hearing and Equilibrium

• Sound Perception: Vibrations move the basilar membrane; hair cells detect pitch and volume.

• Static Equilibrium: Sensed by vestibule; detects head position.

• Dynamic Equilibrium: Sensed by semicircular canals; detects rotational movement.

• Cupula of Crista Ampullaris: Detects angular acceleration.

Special Senses: Chemoreceptors and Taste

• Olfactory Receptors: Detect odors; located in nasal epithelium.

• Taste Buds: Detect sweet, sour, salty, bitter, umami.

Homeostatic Imbalances

• Presbycusis: Age-related hearing loss.

• Myopia: Nearsightedness; focal point in front of retina.

• Hyperopia: Farsightedness; focal point behind retina.

Chapter 9: Endocrine System

Overview of the Endocrine System

The endocrine system regulates body functions through hormones released into the bloodstream. It works closely with the nervous system to maintain homeostasis.

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

• Hormone: Chemical messenger secreted by endocrine glands.

Hormone Classifications

• Amino Acid-Based Hormones: Most hormones; water-soluble.

• Steroid Hormones: Derived from cholesterol; lipid-soluble.

• Eicosanoids: Local hormones; derived from fatty acids.

Hormone Mechanisms and Target Cells

• Target Cell: Cell with specific receptors for a hormone.

• Hormone-Receptor Interaction: Required for hormone action.

• Second Messenger Systems: Used by water-soluble hormones.

Major Endocrine Glands and Hormones

• Pituitary Gland: Releases growth hormone (GH), prolactin (PRL), follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), antidiuretic hormone (ADH), oxytocin.

• Thyroid Gland: Produces thyroxine (T4), triiodothyronine (T3), calcitonin.

• Parathyroid Glands: Secrete parathyroid hormone (PTH).

• Adrenal Glands: Cortex produces corticosteroids; medulla produces epinephrine and norepinephrine.

• Pancreas: Islets secrete insulin and glucagon.

• Pineal Gland: Produces melatonin.

• Gonads: Ovaries produce estrogen and progesterone; testes produce testosterone.

• Placenta: Produces human chorionic gonadotropin (hCG) during pregnancy.

Hormonal Stimuli

• Hormonal Stimuli: Hormones stimulate other endocrine glands.

• Humoral Stimuli: Changes in blood levels of ions/nutrients trigger hormone release.

• Neural Stimuli: Nerve fibers stimulate hormone release.

Homeostatic Imbalances

• Diabetes Mellitus: Insulin deficiency or resistance; high blood glucose.

• Adrenal Disorders: Overproduction or underproduction of corticosteroids.

• Thyroid Disorders: Hyperthyroidism, hypothyroidism.

Sample Table: Major Endocrine Glands and Their Hormones

Gland	Hormone(s)	Main Function
Pituitary (anterior)	GH, PRL, FSH, LH, TSH, ACTH	Growth, lactation, reproduction, thyroid/adrenal regulation
Pituitary (posterior)	ADH, Oxytocin	Water balance, uterine contraction
Thyroid	T3, T4, Calcitonin	Metabolism, calcium regulation
Parathyroid	PTH	Calcium regulation
Adrenal Cortex	Corticosteroids	Stress response, metabolism
Adrenal Medulla	Epinephrine, Norepinephrine	Fight-or-flight response
Pancreas	Insulin, Glucagon	Blood glucose regulation
Pineal	Melatonin	Sleep-wake cycles
Ovaries/Testes	Estrogen, Progesterone, Testosterone	Reproduction
Placenta	hCG	Maintains pregnancy

Additional info: These notes expand upon the study guide questions by providing definitions, examples, and context for each major topic. For exam preparation, students should be able to describe structures, functions, and mechanisms, and apply knowledge to clinical scenarios.