Transcript Unit 10 The Human Body - Jamestown School District

Unit 10 The Human Body
Ch. 35 Nervous System
Organization of the Body
The levels of organization in a
multicellular organism include cells,
tissues, organs, & organ systems
Organization of the Body
Cells:
A cell is the basic unit of structure &
function in living things
Specialized cells - cells uniquely suited to
perform a particular function
Organization of the Body
Tissues:
There are 4 basic types of tissue in the
human body: epithelial, connective,
nervous, & muscle
Epithelial tissue - includes glands & tissues
that cover interior & exterior body surfaces
Organization of the Body
Tissues:
Connective tissue - provides support for
the body & connects its parts
Nervous tissue - transmits nerve impulses
throughout the body
Muscle tissue - along with bones, enables
the body to move
Maintaining Homeostasis
Homeostasis -the process of keeping
internal conditions relatively constant
despite changes in external
environments
Nonliving systems also keep environ.
conditions within a certain range
Maintaining Homeostasis
Negative Feedback - Feedback
Inhibition - when a stimulus produces a
response that opposes the original
stimulus
Ex.) Thermostat regulating room temp,
Pancreas releasing insulin
Negative Feedback
The Nervous System
The nervous system controls &
coordinates functions throughout the
body & responds to internal & external
stimuli
Neurons
Messages carried by the nervous
system are electrical signals called
impulses
Neurons - cells that transmit impulses
Cell Body - largest part of a neuron,
contains the nucleus & most of the
cytoplasm, where the metabolic activity
of the cell takes place
Neurons
Dendrites - short, branched extensions,
that carry impulses from the environ. or
from other neurons toward the cell body
Axon - long fiber that carries impulses
away from cell body
Myelin sheath - insulating membrane
that surrounds the axon
Neurons
The Nerve Impulse
Resting potential - the electrical charge
across the cell membrane of a neuron in
its resting state
An impulse begins when a neuron is
stimulated by another neuron or by the
environ.
The Nerve Impulse
Action potential - the reversal of
charges from the resting state, from “-”
to “+”, also called a nerve impulse
Threshold - the minimum level of a
stimulus that is required to activate a
neuron
The Nerve Impulse
The Synapse
Synapse - the location where a neuron
can transfer an impulse to another cell
Neurotransmitters - chemicals used by
a neuron to transmit an impulse across
a synapse to another cell
Divisions of the Nervous
System
The peripheral nervous system (PNS)
receives info. from the environ. & relays
commands from the CNS to organs & glands
The central nervous system (CNS) relays
messages, processes information, & analyzes
information
The CNS is the control center of the body,
includes the brain & spinal cord
The Central Nervous System
Meninges - layers of connective tissue
that are wrapped around the brain &
spinal cord
Cerebrospinal fluid - bathes the brain &
spinal cord & acts as a shock absorber
that protects the CNS
Brain
The brain consists of the cerebrum,
cerebellum, & brain stem
Brain
Cerebrum - the largest region of the
human brain
It is responsible for the voluntary, or
conscious, activities of
the body
Brain
Cerebellum - the 2nd largest region of
the brain
It is located at the back of the skull
The cerebellum coordinates & balances
the actions of the muscles so that the body
can move gracefully & efficiently
Brain
Brain stem - connects the brain & spinal cord
It is located below the cerebellum, it includes 2
regions: the pons & the medulla oblongata
Each of these regions regulates the flow of info.
between the brain & the rest of the body
Controls important functions like: blood pressure,
heart rate, breathing, & swallowing
Brain
The thalamus & hypothalamus are
found between the brain stem & the
cerebrum
Thalamus - receives messages from all
of the sensory receptors throughout the
body & then relays the info. to the
proper region of the cerebrum for further
processing
Brain
Hypothalamus - the control center for
recognition & analysis of hunger, thirst,
fatigue, anger, & body temperature
It also controls the coordination of the
nervous & endocrine systems
The Spinal Cord
Certain kinds of info., including some
kinds of reflexes, are processed directly
in the spinal cord
Reflex - a quick, automatic response to
a stimulus; it allows your body to
respond to danger immediately, without
spending time to think about a response
Ex.) sneezing & blinking
The Peripheral Nervous
System
The sensory division of the PNS transmits
impulses from sense organs to the CNS
The motor division transmits impulses from
the CNS to the muscles or glands
The somatic nervous system regulates
activities that are under conscious control,
such as movement of the skeletal muscles
The Peripheral Nervous
System
The autonomic nervous system
regulates activities that are automatic
Ex.) Heart rate increases as you run
Overall, the PNS transmits impulses
from sense organs to the CNS & back
to muscles or glands
The Senses
Sensory receptors - neurons that react
to a specific stimulus such as light or
sound by sending impulses to other
neurons, & eventually to the CNS
There are 5 general categories of
sensory receptors: pain receptors,
thermoreceptors, mechanoreceptors,
chemoreceptors, & photoreceptors
The Senses
Pain receptors are found throughout the
entire body, except the brain, & respond
to chemicals released by damaged cells
Pain usually indicates danger, injury, &
disease
The Senses
Thermoreceptors are found in the skin,
body core, & hypothalamus
They also detect variations in temperature
The Senses
Mechanoreceptors are found in the skin,
skeletal muscles, & inner ears
They are sensitive to touch, pressure,
stretching of muscles, sound, & motion
The Senses
Chemoreceptors are found in the nose
& taste buds, & are sensitive to
chemicals in the external environ.
Photoreceptors are found in the eyes, &
are sensitive to light
Vision
Eyes are sense organs used to detect
light
The iris is the colored part of the eye
The pupil is in the middle of the iris
Muscles in the iris regulate the amount
of light that enters the eye
Vision
Lens - located just behind the iris,
muscles attach to the lens to change its
shape, to help you adjust your eyes’
focus to see near or distant objects
Retina - where light is focused onto
from the lens; here, light energy is
converted into nerve impulses that are
carried to the CNS
Vision
Hearing & Balance
Sound is nothing more than vibrations in
the air around us
The ears are the sensory organs that
can distinguish both the
pitch & loudness of
those vibrations
Hearing & Balance
Ears contain structures that help your
CNS maintain your balance, or
equilibrium; they monitor your head in
relation to gravity
Smell & Taste
Taste buds - sense organs that detect
taste
Chemoreceptors found in the taste buds
are sensitive to
chemicals in food
Touch & Related Senses
The sense of touch is not found in just 1
place
All of the regions of the skin are
sensitive to touch
Skin is the largest sense organ of the
body
It contains sensory receptors that
respond to temp., touch, & pain
Drugs & the Nervous System
Drug - any substance, other than food,
that changes the structure & function of
the body
Drugs That Affect the Synapse
Stimulants - drugs that increase the
actions regulated by the nervous
system
They increase heart rate, blood pressure,
& breathing rate
Includes: amphetamines, cocaine, nicotine,
& caffeine
Drugs That Affect the Synapse
Depressants - drugs that decrease the
rate of functions regulated by the brain
They slow down heart rate & breathing
rate, lower blood pressure, relax muscles,
& relieve tension
Includes: Barbiturates, & tranquilizers
Drugs That Affect the Synapse
Cocaine causes the sudden release in
the brain of a neurotransmitter called
dopamine
Its normally released when a need such as
hunger or thirst, is fulfilled
By fooling the brain, cocaine produces
intense feelings of pleasure & satisfaction
Drugs That Affect the Synapse
Opiates mimic natural chemicals in the
brain known as endorphins, which
normally help to overcome sensations
of pain
The first doses produce
feelings of pleasure & security
Drugs That Affect the Synapse
Marijuana produces a temporary feeling
of euphoria & disorientation
Smoking marijuana is more destructive to
your lungs than smoking tobacco
Long-term use can result in memory loss;
inability to concentrate; & in males,
reduced levels of the hormone
testosterone
Drugs That Affect the Synapse
Alcohol is a depressant that slows down
the rate at which the CNS functions
It slows down reflexes, disrupts
coordination, & impairs judgment
Drugs That Affect the Synapse
Fetal alcohol syndrome - a group of
birth defects caused by the effects of
alcohol on the fetus
Babies born with FAS can suffer from heart
defects, malformed faces, delayed growth,
& poor motor development
Drug Abuse
Drug abuse - the intentional misuse of
any drug for nonmedical purposes
Addiction - an uncontrollable
dependence on a drug