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Biology
The Nervous System
Two main parts:
– Central Nervous System
Consists of the brain and spinal cord
– Peripheral Nervous System
Consists of nerve cells that send messages
between the central nervous system and all the
parts of the body
Neurons
Neurons- nerve cells
– Send and receive messages from other
structures in the body such as muscles and
glands
Neurons
Components of a neuron
– 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
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?
Neurons send messages across synapses
through the release of neurotransmitters
– Chemicals that are stored in sacs in the axon
terminal
Nerve Impulses
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
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
2 major parts
– Central Nervous System- brain and spinal
cord
– Peripheral Nervous System- connects brain,
spinal cord to every other part of the body
Brain
Areas of the Brain
– 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
Parts of the Brain
– 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
Brain
Lobes of the Brain
– 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 movementattention, goal-directed behavior, and appropriate
emotional experiences
Brain
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
Peripheral Nervous System
Carries messages to and from the Central
Nervous System
Made of two major parts
– Somatic Nervous System
– Autonomic Nervous System
Somatic Nervous System
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
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
– Both are involved in controlling and integrating
actions of the glands and smooth muscles
Sympathetic and Parasympathetic
Nervous Systems
Sympathetic
– Tell the body to prepare for
an emergency
Heart pounds, breathe
faster, pupils enlarge, &
digestion stops
Tells the endocrine system
to release chemicals into
bloodstream
Connect to every internal
organ of body
Parasympathetic
– Calms the body down
after stress
The Endocrine System
Consists of glands which secrete
hormones into the bloodstream
– Hormones- stimulate growth and affect
behavior and emotional reactions
produced by different glands- pituitary, thyroid,
adrenal, testes, and ovaries
Pituitary Gland
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
Thyroid Gland
Produces thyroxin
– Affects the body’s metabolism- the rate of
converting food to energy
– Low production can lead to hypothyroidismcan cause people to be overweight
– High production can lead to hyperthyroidismcan cause excitability, inability to sleep, and
weight loss
Adrenal Gland
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
– Arouse the body for an emergency
– Adrenaline- can intensify emotions (fear & anxiety)
– Noradrenaline- raises blood pressure
Testes and Ovaries
Testes- males
Ovaries- females
Each produces hormones- testosterone,
estrogen, and progesterone
Testosterone
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
– Primary sex characteristics- directly involved in
reproduction
– Secondary sex characteristics- distinguish males from
females
Estrogen & Progesterone
Female sex hormones but small amounts
are found in males
Females- ovaries produce estrogen and
progesterone
Males- testes produce estrogen and
progesterone
Estrogen & Progesterone
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
– Changing levels of estrogen are linked to PMS
– Estrogen is connected to cognitive functioning and
feelings of well-being among women