Chapter 25 Communication & Control

Section 1 The Nervous System Objectives: Describe the relationship between the central nervous system and the peripheral nervous system. Compare the somatic nervous system with the autonomic nervous system. List one function of each part of the brain.

Two Systems Within a System The nervous system acts as the body’s central command post. The two parts of the nervous system include: central nervous system (CNS) peripheral nervous system (PNS)

The Central Nervous System consists of the brain and spinal cord processes and responds to all messages coming from the peripheral nervous system (PNS)

The Peripheral Nervous System consists of all parts of the nervous system except for the brain and spinal cord connects all parts of the body to the central nervous system (CNS) using specialized structures called nerves A nerve is a collection of axons bundled together with blood vessels and connective tissue.

The Peripheral Nervous System Messages about your environment travel through the nervous system along neurons. A neuron is a nerve cell that is specialized to transfer messages in the form of fast-moving electrical energy. These electrical messages are called impulses.

Neuron Structure

Neuron Structure Cell body-large region in the center of a neuron that has a nucleus and organelles Dendrites-short, branched extensions of the cell that receive information from other cells Axons-elongated extensions of a neuron that carry impulses away from the cell body

Types of Neurons Sensory neurons-gather information about what is happening in and around your body and send to the CNS for processing Motor neurons-neurons that send impulses from the brain and spinal cord to other systems Divided into two types of nerves: Somatic Autonomic

Somatic Nervous System Most neurons are under your conscious control Stimulate skeletal muscles to perform voluntary movements like writing, talking, smiling, and jumping.

Autonomic Nervous System These nerves do not need your conscious control Controls body functions that you don’t think about such as digestion and heart rate Main job is to keep the body’s functions in balance (homeostasis) 2 divisions: sympathetic & parasympathetic

Central Nervous System The largest organ in the nervous system is the brain. It controls both involuntary and voluntary processes. 3 Main Parts: Cerebrum Cerebellum Medulla

Brain Functions Cerebrum – largest part of brain, controls voluntary muscles, thinking, learning, memory, and senses Cerebellum – coordinates muscle movement and balance Medulla – top of brainstem, controls automatic things like breathing, heart beat, and involuntary muscles (digestion)

The Spinal Cord Made of neurons and bundles of axons that pass impulses to and from the brain. The nerve fibers in your spinal cord allow your brain to communicate with your PNS. Surrounded by protective bones called vertebrae.

Section 2 Responding to the Environment Objectives: List four sensations that are detected by receptors in the skin. Describe how a feedback mechanism works. Describe how light relates to sight. Describe how the senses of hearing, taste, and smell work.

Your Five Senses Touch Sight Hearing Taste Smell

Sense of Touch A reflex is an immediate involuntary action. Touch is what you feel when sensory receptors in the skin are stimulated. Four sensations detected by receptors in the skin: vibration pressure pain heat A reflex is an immediate involuntary action.

Feedback Mechanisms A feedback mechanism is a cycle of events in which information from one step controls or affects a previous step.

Sense of Sight Sight is the sense that allows you to see the size, shape, motion, and color of objects around you. Photoreceptors are special neurons in your eyes that change light into electrical impulses. Two types: rods (black & white) & cones (color)

Sense of Hearing Sound is produced when something vibrates. Ears are organs specialized for hearing; each ear has an outer, middle, and inner portion.

Sense of Taste Taste is the sense that allows you to detect chemicals and distinguish flavors. Your tongue is covered with tiny bumps called papillae that contain taste buds. Taste cells in your taste buds react to four basic tastes: sweet, sour, salty & bitter

Sense of Smell Receptors for smell are located on olfactory cells in the upper part of your nasal cavity; they respond to chemical molecules in the air. Taste buds and olfactory cells work together to give you sensations of flavor.

Section 3 The Endocrine System Objectives: Explain why the endocrine system is important to the body. Identify five glands of the endocrine system, and describe what their hormones do. Describe how feedback mechanisms stop and start hormone release. Name two hormone imbalances.

The Endocrine System controls body functions by using chemicals that are made by the endocrine glands Examples include: fluid balance growth development A gland is a group of cells that make special chemicals for your body.

The Endocrine System A hormone is a chemical messenger made in one cell or tissue that causes a change in another cell or tissue in another part of the body. Hormones flow through the bloodstream to all parts of the body.

Major Glands of the Endocrine System Pituitary Gland Anterior and Posterior Pineal Gland Hypothalamus Thyroid Gland Parathyroid Thymus Adrenal Gland Adrenal Cortex Adrenal Medulla Pancreas (Pancreatic Islets) Testes Ovaries

Hypothalamus Location: lies within the diencephalon, below the thalamus; Primary Hormones: No one specific hormone; called the “gate-keeper” regulating the release and inhibition of hormones Functions: “gate-keeper” role; regulates pituitary Major Disorders:

Pituitary Gland Location: Posterior to the hypothalamus Primary Hormones: 9 primary hormones including GH, ACTH, TSH, FSH, LH, ADH and Oxytocin Functions: Secretion of essential endocrine hormones; “the master gland”; Major Disorders: dwarfism, gigantism, Diabetes encephalis

Pineal Gland Location: Between the pons and sides of the thalamus; size of a pea Primary Hormones: Melatonin Functions: Regulates sleep patterns; mating patterns; migration patterns; day and night rhythms Major Disorders: Insomnia

Thyroid Gland Location: Anterior region of neck, surrounding trachea Primary Hormones: Thyroxine (T-4) and Triiodothyronine (T-3) Functions: Regulate iodine; secrete TSH (thyroid stimulating hormone) Major Disorders: Goiter; Thyroid Cancer

Parathyroid Gland Location: 4 glands around the thyroid Primary Hormones: PTH (parathyroid hormone) Functions: Affects the bones and kidneys; maintain calcium levels in the blood Major Disorders: Osteoporosis; Hyper- and Hypo- parathyroidism

Thymus Location: Thoracic cavity below the neck; Primary Hormones: Thymosis; Functions: T-lymphocyte education center Major Disorders: Cancers (lymphomas)

Adrenal Gland Adrenal Cortex Location: Atop the kidneys; outer layer surrounding the adrenal medulla Primary Hormones: Glococorticoids, Mineralcorticoids, and Aldosterone Functions: Maintain blood pressure, metabolism, levels of estrogen and testosterone Major Disorders: Addison’s disease and Cushing’s disease

Adrenal Gland Adrenal Medulla Location: Atop the kidneys surrounded by the adrenal cortex; the adrenal pulp Primary Hormones: Epinephrine and Norepinephrine (a.k.a. Adrenaline) Functions: Increase blood pressure, heart rate, dialation of pupils (adrenaline rush) Major Disorders: Pheochromocytoma

Pancreas Location: Around the stomach and small intestine Primary Hormones: Insulin and Glucagon (secreted by the pancreatic islets or the Islets of Langerhans) Functions: Digestion of enzymes; regulate blood-glucose levels; insulin uptake Major Disorders: Diabetes mellitus types I and II

Testes Location: Within the scrotum Primary Hormones: Testosterone; ICSH Functions: Produce sperm and testosterone; primary and secondary sex characteristics Major Disorders: Testicular cancer; Germ-cell tumors

Ovaries Location: In the abdomen at the end of the fallopian tubes Primary Hormones: Estrogen, Progestins, Estradiol Functions: Produce female gametes; ova and ovum; oocytes- immature gametes Major Disorders: Ovarian Cancer;