Regulation of Body Processes

• Responses to both internal and external stimuli must be regulated and coordinated

• These responses are controlled by the body’s nervous and endocrine systems

• Nervous System: – sends electrochemical signals using neurons

• Endocrine System: – sends chemical signals by using hormones

secreted by glands.

Mechanisms of Nervous Regulation

• Receptors: – sensory organs with

specialized structures that are sensitive to changes or “stimuli”

– When stimulated, receptors cause impulses to be carried both electrically and chemically between nerve cells.

– Sensory Organs Include: • eyes, nose, skin, taste buds, ears

– Stimuli They Respond to:• Physical forces

– Ex: heat, cold, pressure, light

• Chemical changes – inside and outside organism

• Effectors: specialized structures that respond to commands of nervous system– gland (increases or decreases secretion)– muscle (contracts)

Nerve Cells (Neurons)

• Carry electrochemical messages or impulses from receptor to effector

– Stimulus occurs– Receptor senses stimulus– Impulses sent along nerve

pathway– Effector responds

• Nerve = many neurons bundled together

Types of Neurons• Sensory Neurons

– Carry impulses from receptors to spinal cord and brain

• Motor Neurons– Carry impulses from brain and spinal cord to effectors (muscles)

• Interneurons– Relay impulses between neurons, (found in brain and spinal cord)

Basic Neuron Structure• Cell Body:

– contains nucleus and cell organelles– Carries out metabolic activities and controls growth

• Dendrites: – short highly branched fibers – receive impulses

• Axon: – long thin fiber that extends away from cell body– Carries impulses from dendrites to terminal branches

• Schwann Cells: – Surround axons of many vertebrates– Produce myelin which forms an insulating covering

around axon– Gaps between cells are called Nodes of Ranvier

• Terminal Branches: – Branches at end of axon – End in “synaptic knobs” that

contain neurotransmitters– They lie very close to

dendrites of other neurons – Chemical communication of

a nerve impulse happens between neurons here

• Synapse: – small gap between synaptic

knob of one neuron and dendrite of another

How does Signal Travel Along a Neuron?

Sending a Nerve Impulse• Electrical Signal Travels:

– At rest: nerve membrane is “polarized”• Outside is +, inside is –

– During Impulse:• Switch in polarity travels along the nerve cell

• Myelination of axon helps to insulate the signal and it conducts faster

• Signal can jump quickly between Nodes of Ranvier

Sending a Nerve Impulse• Chemical Communication

Occurs Between Neurons:– Happens at the synapse

• Tiny gap between synaptic knob of one neuron and dendrite of another

– Electrical impulse triggers release of neurotransmitter molecules from vesicles into the synapse

• Ex: acetylcholine, seratonin

• These molecules bind to specific receptor proteins in the membrane of the adjoining neuron

• That neuron will now “fire” and send signal along itself

• Impulses travel in one direction across a synapse

• Synapse and Neurotransmitters:• http://www.youtube.com/watch?v

=p5zFgT4aofA&safe=active

• Note:• Each neurotransmitter

will only bind to a specific receptor that it will “fit”– Certain drugs mimic

the effects of neurotransmitters by binding to these receptor molecules

• Stopping a Signal:– After a signal is sent enzymes at the synapse

break down the neurotransmitters in the synapse or they are reabsorbed back into vesicles.

Electrical, Chemical, Electrical Chemical…

Neuron Firing Animation:http://www.youtube.com/watch?v=90cj4NX87Yk&safe=active

The Neuromuscular Junction

• Synaptic point of contact between motor neurons and muscle cells

• Motor neurons end in “motor end plates” that release the neurotransmitter acetylcholine

• These molecules bind with receptors in membrane of muscle cells causing them to contract.

Drugs and the Synapse

• Certain poisons and drugs can effect activity of neurotransmitters– Ex: nerve gas, botulin toxin

(botox), insecticides, venom

• Can cause muscular paralysis and even death

• Stimulants: speed up nervous response– Caffeine, amphetamines, cocaine

• Depressants: slow down nervous system– alcohol, marijuana, barbiturates

• LSD: (hallucinogenic)– blocks enzyme that removes neurotransmitter serotonin from synapse. – It remains in gap and keeps neurons firing.

The Human Nervous System

• Divided into the:

• Central Nervous System:– Brain– Spinal Cord

• Peripheral Nervous System– Somatic: controls skeletal muscles (voluntary)– Autonomic: controls smooth muscles (involuntary)

Central Nervous System• Brain and Spinal Cord• Receive impulses from

sense receptors

• Interprets information

• Sends impulses for responses to muscles and glands

The Brain• Large mass of neurons

located in the cranial cavity.

• Covered and protected by tough membranes called meninges.

• Cerebrospinal fluid surrounds brain and cushions against shock

• One of the most active organs of the body, major user of glucose!

• Concussion: when brain is severely shaken

• Meningitis: membranes that surround the brain and spinal cord get infected

Parts of the Brain• Cerebrum

– Center for voluntary activity– Interprets sensory impulses– Initiates some motor activities– Responsible for memory,

thinking and reasoning• Cerebellum

– Coordinates motor activities – Aids in maintaining balance

• Medulla– Controls involuntary activities

such as breathing, heartbeat, blood pressure and peristalsis (is part of the brain stem)

– Most “primitive” part of brain

Know the Three Parts of the Brain and What They Do!

Hemispheres of the Brain

Each hemisphere controls the opposite side of the body.

Brain Size and Intelligence

Spinal Cord• Protected by vertebrae of

spinal column and rings of cartilage

• Surrounded by meninges and cerebrospinal fluid

• Coordinates activities between the brain and peripheral nervous system

• The center for reflex action

http://www.youtube.com/watch?v=38zEmPuWd-o&safe=active

Getting a Spinal Tap

Peripheral Nervous System

• All neurons and nerve fibers outside of brain and spinal cord.

• Somatic System• Connects brain and spinal cord to skeletal

muscles, skin and sensory organs• Responsible for voluntary movement• Under conscious control

– Ex: moving arms, legs, watching TV, listening to music

• Autonomic System

• Relays information to and from internal organs

• Involuntary movement

• Not under conscious control

Ex: – Rate of heart beat, breathing,

peristalsis in digestive tract

Turning Responses On and Off

• Sympathetic Nervous System– Generally speeds up autonomic processes– Responsible for “fight or flight” response

• Ex: Urinary Muscles contract, pupils contract, saliva secreted

• Parasympathetic Nervous System– Generally slows things down

• Ex: Urinary Muscles relax, pupils dilate, saliva stopped

Somatic vs. Autonomic Muscle

Organ

Reflexes• Involuntary response to a

stimulus– Part of somatic nervous system

• Simple pathway:– Receptor - spinal cord - effector

• Many normal body functions controlled this way– Ex: Blinking, sneezing, coughing

Pupil size in response to light:http://www.youtube.com/watch?v=Yj5-cJgVX3c&safe=active

• Why do doctors check reflexes?– If you do not have a

response to a reflex, something is wrong with your nervous system.

– Ex: Pupils “fixed and dilated”

http://www.youtube.com/watch?v=GgQq79YxuUg&safe=active

• Reflec Arc

• Pathway nerve impulses travel in a reflex

• Simplest have only one sensory neuron and one motor neuron – Ex: knee jerk response

http://www.youtube.com/watch?v=nKPEW-ao2Wg&safe=active

Reflex Arc

• Most reflexes involve 3 or more neurons– Ex:

• hand pulling back from burn or pain (withdrawal reflex)

• Sensory Neuron • Interneuron (in spinal

cord)• Motor Neuron

Reflexes in Babies

http://www.youtube.com/watch?v=lA6EkByW8wk&safe=active

Disorders of the Nervous System

• Polio: viral infection that affects motor function and can cause paralysis

• Stroke: a burst blood vessel in the brain, causing cerebral hemorrhage. Can cause brain damage, paralysis, death

• Cerebral Palsy: birth disorder, causes problems with motor function

• Multiple Sclerosis: myelin coating around neurons degenerates affecting motor function.

• Meningitis: inflammation of membranes surrounding brain or spinal cord.

Adaptations for Nervous Regulation

• Protists– No true nervous system– Can respond to certain stimuli– Can tell food from nonfood, strong light, harmful chemicals– Can respond to irritants in environment– Paramecium have neurofibrils that connect cilia on

membrane and coordinate their beating

Hydra

• Has a nerve net– Nerve cells form a network

between two cells layers of body– Impulses travel in all directions

• Coordinates movement of tentacles to bring in food

• Whole body tend to respond to a stimulus at once

• Time Lapse Video of Hydra Moving• http://www.youtube.com/watch?v=-UI531GMRTM&sa

fe=active

Earthworm• Central Nervous System:

– “brain” connected to pair of ventral nerve cords with ganglia in each segment

• Peripheral Nervous System: – Sensory receptors in skin for light, vibrations, chemicals– Motor neurons from nerve cord to muscles and glands

Grasshopper• Dorsal “Brain” made of

fused ganglia • Ventral nerve cord with

series of fused ganglia• Peripheral nerves

branch from ganglia to muscles, sensory organs

• Complex sensory organs include tympana, eyes, antennae

• Crash Course: The Nervous System

• http://www.youtube.com/watch?v=x4PPZCLnVkA&safe=active