THE HUMAN BODY

Life Processes

Regulation Nutrition Transport Respiration Locomotion Excretion

Organ Systems

Because humans are complex multicellular organisms, organ systems are needed to carry out the major life processes.

Levels of organization:cellstissuesorganssystems

Regulation

The nervous and endocrine systems control and coordinate life activities to maintain homeostasis. This is known as regulation.

Nervous System

Nervous System

Neurons – specialized cells that transmit electrochemical messages called impulses. This is how the body communicates rapidly

producing responses of short duration.

Axon terminals

Myelin sheath

Nodes

Cell body

Axon

Nucleus

Dendrites

Section 35-2

A Neuron

Neuron

Neuron

• Active transport maintains nerve cells in a charged state ready to transmit a message.

• Nerve cells use lots of glucose and have lots of mitochondria.

Active Transport

Synapse

Neurons communicate with each other by secreting chemicals across a tiny gap called the synapse.

Vesicle

Axon

Axon terminal

Synaptic cleft

Neurotransmitter

Receptor

Dendrite of adjacent neuron

Direction of Impulse

Section 35-2

Figure 35-8 The Synapse

Synapse

Used to increase alertness, relieve fatigue

Used to relieve anxiety, irritability, tension

Used to relieve pain

Stimulants

Depressants

Opiates

Amphetamines

BarbituratesTranquilizers

MorphineCodeine

Increase heart and respiratory rates; elevate blood pressure; dilate pupils; decrease appetite

Slow down the actions of the central nervous system; small amounts cause calmness and relaxation; larger amounts cause slurred speech and impaired judgement

Act as a depressant; cause drowsiness, restlessness, nausea

Section 35-5

Commonly Abused Drugs

Drug Type Medical Use Examples Effects on the body

Drugs Affect the Synapse

Nervous System

Central Nervous System Brain & spinal cord

Peripheral Nervous System Nerve branches off the brain and spinal

cord Sense organs

Pons

Pituitary gland

Hypothalamus

Cerebrum

Medulla oblongata Spinal cord

Cerebellum

Pineal gland

Thalamus

Section 35-3

Figure 35-9 The Brain

Brain

Spinal nerve

Central canalGray matter

White matter

Meninges

Section 35-3

Cross Section of the Spinal CordSpinal Cord

Cerebral cortex

Nasal cavity

Taste bud

Smell sensory area

Tastesensory area

Thalamus

Olfactory(smell) bulb

Olfactorynerve

Smell receptor

Taste pore

Taste receptor

Sensorynerve fibers

Section 35-4

The Senses of Smell and TasteSense Organs

Choroid

Retina

Blood vessels

Optic nerve

Fovea

Vitreous humor

Sclera

Ligaments

Iris

Pupil

Cornea

Aqueous humor

Lens

Muscle

Section 35-4

Figure 35-14 The EyeEye

Auditory canal

Tympanum Round window Eustachian tube

Bone

Cochlea

Cochlear nerve

Semicircular canals

Oval window

StirrupAnvilHammer

Section 35-4

Figure 35-15 The EarEar