Regulatory Systems: Nervous

and Endocrine Systems

regulate the activities of the other systems to make sure homeostasis is maintained

(homeostasis: keeping the internal environment of the body constant; for example, body

temperature, blood pressure)

Function of Regulation Systems:

Nervous System

Chemical signals (neurotransmitters) to pass the impulse to the next cell

Uses Electrical signals (impulses) along nerves

Endocrine System

Uses: Hormones made in

glands

The bloodstream for transmission

The NERVOUS SYSTEM

Nervous system Functions:Receive Stimulus Integrate the

InputSend out motor

commands

Neurons - Functional Units

Neurons (aka nerve cells):

•Generate and transmit nerve impulses

•Have three main parts:

•Cell body – contains nucleus and other organelles

•Dendrite – receives impulse from another neuron

•Axon – sends impulses to other neurons, muscles or glands

•The axons of some neurons have a myelin sheath for protection and faster transmission.

Cell body

DendritesAxon

Neurons

Myelin sheath

The impulse is transmitted:

Dendrites

Cell body

Axon

Axon terminal

Sensory neurons sense stimuli caused by changes in the internal or

external environment

Interneurons integrate signals from different parts of the nervous

system

Motor neurons transmit signals to muscles and glands  

Muscles contractGlands secrete substances

Types of Neurons

Types of Neurons

Sensory Neuron

Interneuron

Motor Neuron

The Nerve Impulse

• Transmission of nerve impulses depends upon a difference in charge across the cell membrane.

• The interior of neurons is more negatively charged compared to the outside

This is called its Resting Potential

Channel proteins maintain the polarity

•Sodium ions are concentrated outside of the cell, potassium ions are concentrated inside the cell

The Nerve ImpulseThe transmission of a nerve impulse is rapid and self-

propagating (like dominoes)

The major players:• sodium ions (Na+) usually found outside the cell• potassium ions (K+) usually found inside the cell• sodium protein channels in the cell membrane• potassium protein channels in the cell membrane

The Nerve Impulse

The nerve impulse is transmitted along the neuron by reversing the negative charge along the membrane

Inside becomes more positive than outside

This is called the action potential

As Sodium channels close Potassium channels open and K+ ions leave the cell

Cell is more positive outside

Sodium channels open in the area next to the original action potential, passing the impulse along

Sodium channels open in part of the membrane and Na+ ions enter the cell

Cell is more negative outside

Sodium-Potassium Pump moves 3 sodium ions out of the cell and 2 potassium ions inside the cell, restoring the original positions of ions

The Nerve Impulse

Sodium – Potassium Pump is Active transport:

Moving substances across membrane from lower to higher concentration requires cell to expend energy.

The Nerve Impulse

Saltatory conduction:

Transmission of the action potential in myelated axons (faster than in non myelated axons)

The Nerve Impulse

Summary:• Resting (no impulse): Inside more negative than outside.• Sodium ions (Na+) move inside through protein channels

makes the inside of the cell less negative action potential generated

• The action potential travels along the axon (like dominoes or in jumps (myelated axons)) nerve impulse

• Potassium ions (K+) move outside the cell through protein channels negative charge restored inside the cell

• Sodium-Potassium Pump restores positions of ions (sodium out, potassium in)

Until the position of the ions is restored, the nerve can not carry another impulse

The Nerve Impulse

All or None Principle:A nerve cell will either fire or not fire – once the

impulse begins, it will continue down the cell

Impulse is the same intensity each timeDifferent strengths of stimuli can be detected by:• a different number of nerve cells that fire

– The more cells, the stronger the “message”

• the frequency of the repeated impulse– The faster the impulse is repeated, the stronger the

“message”

The synapse

Synapse:gap in between

an axon terminal and a dendrite

Synapse

Passing the impulse to the next cell

At the end of the terminal branches are vesicles with neurotransmitters

The neurotransmitters are released into the synapse

vesicles

Terminal end

The synapse

The Synapse1. Nerve impulse reaches axon end

2. Neurotransmitter (NT) released into synapse (exocytosis)

3. Neurotransmitter diffuses across synapse

4. Neurotransmitter binds to receptors in the cell membrane of the next neuron

5. Impulse generated at the next neuron.

The Synapse

• Two examples of NT:– Acetylcholine– Norepinephrine

• Certain poisons/drugs interfere with synaptic activity – cause either paralysis or constant stimulation

Two main components:

(1) Central Nervous System (CNS): Brain + Spinal Cord

The Nervous System

(2) Peripheral Nervous System (PNS): nerves outside the CNS

• Functions:

• Integrates & interprets sensory impulses

• Generates motor impulses.

• Consists of the brain and spinal cord

• The spinal cord provides communication between the brain and PNS.

• The Meninges: three continuous sheets of connective tissue covering the spinal cord and brain

Central Nervous System (CNS)

Major Areas of The Brainspeech, vision,

hearing, thought

Sensory inputhunger, thirst, temperature

Balance, posture, coordination Heart beat, breathing

• Two hemispheres• a core of grey

matter covered by white matter

• an outer grey layer (cerebral cortex).

• Four lobes– Frontal– Parietal– Occipital– Temporal

Cerebrum

Phineas Gage (1848)

Lobotomy: destruction of the prefrontal cortex:

Treatment for a wide range of mental illnesses including schizophrenia, clinical depression, and various anxiety disorders.

Functions:Carry sensory impulses from receptors to CNS

Carry motor impulses from CNS to muscles and glands.

Peripheral Nervous System (PNS)

Composed of nerves

(bundle of axons)

Peripheral Nervous System (PNS):

The bundled axons make up the nerves of the PNS

Cell bodies of neurons are found in the CNS or in ganglia present in the PNS

(ganglion = collection of cell bodies)

• The Somatic system – the nerves that convey sensory information to the

CNS – the motor nerves that transmit impulses to muscles– voluntary control as well as involuntary reflexes

• The Autonomic system– involuntary control of glands, cardiac muscle, and

smooth muscle.

Peripheral Nervous System

Divided into Two main Sections:

• Involuntary response, or reflexes, can be mediated by the brain or the spinal cord.

Reflex Arc

Anatomy of the Human Ear

pinna

Hammer (Malleus) Stirrup

(Stapes)

Anvil (Incus)

External Auditory Canal: the tube through which sound travels to the eardrum.

Tympanic membrane (eardrum):

•between the outer and middle ear

•transmits sound waves to middle ear

Anatomy of the Human EarOuter Ear:

Pinna – visible part of ear:•composed of cartilage •presence on both sides of the head allows us to localize the source of sound from the front vs. the back.  

Anatomy of the Human Ear

Ossicles:Hammer - (malleus) passes vibrations from the eardrum to the anvil.Anvil - (incus)passes vibrations from the hammer to the stirrupStirrup - (stapes) U-shaped bone that passes vibrations from the stirrup to the cochlea.

smallest bone in the human body. 

Middle EarEustachian tube (auditory tube) •connects the middle ear to the back of the nose•equalizes the pressure between the middle ear and outside air.

Anatomy of the Human EarInner ear Cochlea •spiral-shaped, fluid-filled structure•lined with cilia (tiny hairs)

•move when vibrated and •cause a nerve impulse to be generated.

Semicircular Canals – •three loops of fluid-filled tubes•attached to the cochlea•help maintain sense of balance.

Auditory Nerves – •carry electro-chemical signals from the inner ear (the cochlea) to the brain.

The spiral organ of the cochlea

To cochlear nerve

Sound Waves to Nerve Impulses

Air pressure waves in the ear canal (sound energy) causes...

Ear drum motion (vibrational energy), which causes...

Motion of the ossicles (vibrational energy), which causes...

Inner ear fluid pressure waves (vibrational energy), which causes…

Nerve impulses within the cochlea, which are then carried via a series of nerve connections to the portion of the brain that perceives "sound," the auditory cortex (electrochemical energy.)

Anatomy of the Eye

Anatomy of the Eye

• Sclera "the white of the eye" – is the tough, opaque tissue that

serves as the eye's protective outer coat

– Completely surrounds eye • Conjunctiva

– thin, transparent tissue that covers the outer surface of the eye. 

– begins at the outer edge of the cornea, covers the visible part of the eye, and lines the inside of the eyelids

– nourished by tiny blood vessels that are nearly invisible to the naked eye.  

Anatomy of the Eye

• Cornea– transparent, dome-shaped

window covering the front of the eye

– a powerful refracting surface

– provides 2/3 of the eye's focusing power

• Pupil– black, circular opening in

the center of the iris. – opens and closes– regulates the amount of

light entering the eyeball

Anatomy of the Eye

• Iris– Colored part of the eye– controls light levels inside

the eye similar to the aperture on a camera. 

– embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size. 

• Lens   – focus light onto the back of

the eye

Anatomy of the EyeVitreous

– thick, transparent substance that fills the center of the eye

– composed mainly of water– comprises about 2/3 of the

eye's volume– gives it form and shape

Retina•Very thin layer of tissue lining the inner part of the eye•captures the light rays that enter the eye•light impulses are then sent to the brain for processing, via the optic nerve.

Anatomy of the Eye

• Choroid– Lies between retina

and sclera– composed of layers of

blood vessels that nourish the back of the eye.

• Optic nerve – transmits electrical

impulses from the retina to the brain. 

Vision• Humans have binocular

vision – Eyes see slightly different

angles– Allows for depth perception

• Two types of photoreceptors in retina– Rods: very sensitive, night

vision– Cones: detect bright light,

colors, detail

Light Waves to Nerve Impulses• Light energy passes

through the pupil• Lens focuses light on

photoreceptors in the retina• Photosensitive pigments

are split and release energy• Electrochemical signal

generated • Intermediate cells in the

retina integrate signals• Signal is passed on to the

optic nerve • Nerve impulses sent to the

brain for processing into an image