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 FunctionsCerebrum – 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• 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 SystemObjectives:• 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 GlandAdrenal 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 GlandAdrenal 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;