Nervous & Endocrine System

Peripheral Nervous System (PSN)

The portion of the nervous system outside the brain and spinal cord ; divided into somatic and autonomic divisions

Sympathetic Nervous System

Prepares the body for fight-or-flight response: increases heart rate, blood pressure, and metabolic activity during stress or danger

Neuron Anatomy

Basic functional unit of the nervous system consisting of the cell body, dendrites (receive signals), and axon (transmit signals)

Axons

Long extensions of neurons that carry the nerve impulse away from the body to other neurons or target tissues

Neuroglial Cells

Support cells that provide structure and insulation; produce myelin, which increases the speed of nerve impulses transmission

Frontal Lobe

Controls voluntary movement, speech, and decision-making

Parietal Lobe

Processes sensory information (touch, temp, pain)

Temporal Lobe

Processes hearing and memory

Occipital Lobe

Processes vision

Speed Comparison

The nervous system responds much quicker than the endocrine system (seconds vs minutes to hours)

Specificity

The nervous system has higher specificity than the endocrine system; nervous signals target neurons, while hormones affect multiple tissues

Functions of Glands

Endocrine glands produce and secrete hormones directly into the bloodstream to regulate physiological processes in target issues

Hypothalamus-Pituitary Axis

The primary control center for hormone regulation in the body

Hypothalamus

Produces releasing hormones; its target tissue is the anterior pituitary

Infundibulum

The stalk connecting the hypothalamus to the pituitary gland

Anterior Pituitary Functions

Produces thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), growth hormone (causes widespread tissue growth), and luteinizing hormone (stimulates sperm production)

Posterior Pituitary

Releases antidiuretic hormone (ADH), which promotes water retention and decreases urine production

General Hormone Categories

Steroids, amino acid derivatives, proteins, and peptides

Thyroid Glands

Bow-tie shaped gland located anterior or lateral to the trachea below the larynx; produces thyroid hormone, which increases metabolic rate and promotes tissue growth

Parathyroid Glands

Small glands embedded in the thyroid secrete parathyroid hormone (PTH), which regulates calcium levels

Adrenal Glands

Sit atop the kidneys; secrete epinephrine (adrenaline) from the medulla

Epinephrine Functions

Raises metabolic rate, increases heart rate, increases blood insulin, which regulates blood glucose levels

Medical Terminology

Use adren/o or adrenal/o (NOT aden/o, which means gland)

Pancreas

Dual-role organ functioning in both endocrine and digestive systems; produces insulin, which regulates blood glucose levels

Pineal Gland

Produces melatonin, which regulates sleep-wake cycles

Target Tissue Sensitivity

Regulated by changing the number of receptors present on target cells

Up-regulation

Increase in the number of receptors for a hormone, making cells more responsive

Down-Regulation

Decrease in the number of receptors for a hormone, making cells less responsive

Hormone Elimination Methods

Metabolism, Excretion, Conjugation

Half-Life

The time required for one-half of a substance to be eliminated from the circulatory system varies by hormone

NOT a Method of Elimination

Passive transport does not eliminate hormones from circulation

Diabetes Mellitus

Inability to regulate blood glucose due to insufficient insulin production or insulin resistance

Addison’s Disease

Characterized by adrenal cortex degeneration, resulting in inadequate hormone production

Grave’s Disease

Autoimmune thyroid disorder causing excessive thyroid hormone production (hyperthyroidism)

Polyuria

Excessive urination

Polydipsia

Excessive thirst

Glucosuria

Presence of glucose in urine

Andr/o

Male

Gluc/o and glyc/o

Both means sugar

Aden/o

Means gland (NOT adrenal gland)

Autocrine Signaling

A cell produces a hormone that signals to itself, allowing for self-regulation

Paracrine Signaling

A cell produces a hormone that signals to nearby cells in the local area

Endocrine Signaling

A cell produces a hormone that travels through the bloodstream to signal a distant target tissue

Pheromones

Chemical signals released by organisms that influence behavior or physiology in other organisms (relevant to perfume and fragrance industries)

Speed of Response

Very fast (milliseconds to seconds); Slower (minutes to hours)

Specificity

High specificity to the target neurons; Lower specificity, affects multiple tissues

Duration of Effect

Brief, effects stop quickly; Long-lasting, effects persist longer