Transcript Biology The Nervous System

Biology
The Nervous System
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Two main parts:
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Central Nervous System
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Consists of the brain and spinal cord
Peripheral Nervous System
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Consists of nerve cells that send messages between the
central nervous system and all the parts of the body
Neurons
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Neurons- nerve cells
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Send and receive messages from other structures in
the body such as muscles and glands
Neurons
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Components of a neuron
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Cell Body- produces energy that fuels the activity of the cell
Dendrites- thin fibers which branch out of the cell, receive
information from other neurons and pass the message
through the cell body
Axon- carries messages away from the neuron, single fiber
Myelin- covering of the axon, insulates and protects the axon,
helps to speed up the transmission of the message
Axon terminal- small fibers branching out from an axon
Types of Neurons
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Sensory- carry messages from sense organs to
spinal cord or brain
Motor- carry messages from spinal cord or brain
to muscles or glands
Interneurons- carry messages from one neuron
to another and do most of the work of the
nervous system
How do Neurons communicate?
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Neurons send messages across synapses through
the release of neurotransmitters
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Chemicals that are stored in sacs in the axon
terminal
Nerve Impulses
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Absolute refractory period- after one cell firing,
it will not fire again regardless of how strong the
incoming message is
Relative refractory period- time when neuron is
returning to normal and may refire if message is
stronger then usual
All or none law- a neuron fires at full capacity or
does not fire at all
Firing of a nerve cell
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Dendrite or cell body picks up message
If message is strong enough, neuron fires and
impulse starts down the axon
Out the end of the axon terminal to the synaptic
knob
On to the next nerve cell
Central Nervous System
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2 major parts
Central Nervous System- brain and spinal cord
 Peripheral Nervous System- connects brain, spinal
cord to every other part of the body
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Brain
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Areas of the Brain
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Hindbrain- co-ordinate motor activity, posture, equilibrium,
sleep patterns, and regulate unconscious functions (ex. blood
circulation and breathing)
Midbrain- vision, hearing, motor control, sleep/awake cycle,
arousal (alertness), and temperature regulation
Forebrain- controls cognitive, sensory, and motor functions,
regulate body temperature, reproductive functions, eating,
sleeping, and display of emotions
Brain
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Parts of the Brain
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Amygdala- storing & classifying emotional memories,
produces emotions
Hippocampus- memory formation, classifying information,
long-term memory
Thalamus- sensory signals, visual information, information
from skin and internal organs, motor control
Hypothalamus- metabolic processes, body temperature,
hunger, thirst, fatigue, anger, and circadian cycles
Brain
Cerebellum- regulates & coordinates movement,
posture, and balance
 Pons- relays messages to other parts of the brain,
controls arousal, and respiration
 Medulla Oblongata- heart rate, respiration, blood
pressure, swallowing, vomiting, and defecation, relay
station for nerve signals going to/from the brain
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Brain
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Lobes of the Brain
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Occipital- receives and interprets visual information
Temporal- controls hearing and some processing of visual
and olfactory information
Parietal- responds to sensations of touch bodily position
Frontal- responsible for voluntary movement- attention, goaldirected behavior, and appropriate emotional experiences
Brain
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Hemispheres
Left- right-hand touch and movement, speech,
language, and writing
 Right- left-hand touch and movement, spatial
construction, non-verbal imagery, and face
recognition
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Peripheral Nervous System
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Carries messages to and from the Central
Nervous System
Made of two major parts
Somatic Nervous System
 Autonomic Nervous System
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Somatic Nervous System
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Composed of all sensory (afferent) neurons that
carry information to the CNS and all the motor
(efferent) neurons that carry messages from the
CNS to the skeletal muscles of the body
The senses have their origin in the somatic part
of the Peripheral Nervous System
Autonomic Nervous System
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Composed of all the neurons that carry messages
between the CNS and all the internal organs of the
body (glands and smooth muscles such as the heart and
digestive system)
Important in breathing, blood flow, and emotions
Has two branches- sympathetic and parasympathetic
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Both are involved in controlling and integrating actions of
the glands and smooth muscles
Sympathetic and Parasympathetic
Nervous Systems
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Sympathetic
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Tell the body to prepare for an
emergency
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Heart pounds, breathe faster,
pupils enlarge, & digestion
stops
Tells the endocrine system to
release chemicals into
bloodstream
Connect to every internal
organ of body
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Parasympathetic
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Calms the body down after
stress
The Endocrine System
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Consists of glands which secrete hormones into
the bloodstream
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Hormones- stimulate growth and affect behavior
and emotional reactions
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produced by different glands- pituitary, thyroid, adrenal,
testes, and ovaries
Pituitary Gland
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Lies below the hypothalamus
Considered the “Master Gland”
Secretes different hormones
Growth- regulates growth of muscles, bones, and
glands
 Prolactin- stimulates production of milk in nursing
women
 Oxytocin- stimulates labor in pregnant women
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Thyroid Gland
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Produces thyroxin
Affects the body’s metabolism- the rate of
converting food to energy
 Low production can lead to hypothyroidism- can
cause people to be overweight
 High production can lead to hyperthyroidism- can
cause excitability, inability to sleep, and weight loss
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Adrenal Gland
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Located above the kidneys
Secretes cortical steroids- increase the resistance to
stress and promote muscle development, can cause the
liver to release stored sugar in emergencies
Produce adrenaline and noradrenaline
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Arouse the body for an emergency
Adrenaline- can intensify emotions (fear & anxiety)
Noradrenaline- raises blood pressure
Testes and Ovaries
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Testes- males
Ovaries- females
Each produces hormones- testosterone,
estrogen, and progesterone
Testosterone
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Testosterone- male sex hormone, small amount
found in females
Influences the development of sex organs (if secreted
child will be male, if not- female)
 Aids in growth of muscle and bone, primary and
secondary sex characteristics
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Primary sex characteristics- directly involved in reproduction
Secondary sex characteristics- distinguish males from females
Estrogen & Progesterone
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Female sex hormones but small amounts are
found in males
Females- ovaries produce estrogen and
progesterone
Males- testes produce estrogen and
progesterone
Estrogen & Progesterone
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Estrogen-Development of primary and secondary sex
characteristics
Progesterone- stimulates growth of female
reproductive organs and prepares the body for
pregnancy
Both regulate menstrual cycle and vary during the cycle
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Changing levels of estrogen are linked to PMS
Estrogen is connected to cognitive functioning and feelings
of well-being among women