• Answer

Does your heart stop when you sneeze?

Human Regulation

Coordination and Control

Regulation in Humans

• Controlled by 2 systems– Nervous System - electrical– Endocrine System – chemical

• Both systems respond to and send messages throughout the body

Human Nervous System

Central and Peripheral

A General Sense…

Peripheral Nervous System

Central Nervous System -Brain -Spinal Cord

Motor Neurons-carry signals away from CNS

Sensory Neurons-carry messages towards spinal cord from sensory receptors

Somatic System: Voluntary Nerves--neurons control skeletal muscles

Autonomic System:Visceral, Involuntary--heart, blood vessels, digestive organs, smooth muscle

Sympathetic Division--“fight or flight”--activated by stress

Parasympathetic Division:--Routine

An Overview of the Nervous System:

Nervous System Cells

• Called neurons

• Neurons have long axons that enable them to transmit signals. Many neurons together are called a nerve.

• Each nerve has a dorsal root (info coming into the CNS) and a ventral root (info going out from CNS to body).

Anatomy of a Neuron

• Cell body – main part• Dendrite – receives action potential (stimulation) from

other neurons• Axon – branches from cell body, where the action

potential occurs• Axon terminal – end of an axon• Myelin sheath – lipid layer for protection over neurons that

allows for increase in speed of signal transmission; made by Schwann cells

• Nodes of Ranvier – gaps in myelin sheath along the axon, where most Na+ pumps are located

• Synaptic Cleft – gap between neurons; between the axon terminal of 1 neuron and the dendrite of a 2nd neuron

Anatomy of a Neuron

Central Nervous System (CNS)

BRAIN• About 1.4 kg, 2% of body weight• About 100 billion neurons• 12 pairs of cranial nerves are connected to

the human brain– Example: Pupil reflex in response to bright

light, to avoid damage to retina. Nerves that control this reflex are connected to the brain.

Spinal Cord• Starts at the medulla

oblongata (in the brain)• Outer area is made up

of the axons of motor and sensory neurons: “white matter”

• Inner, rigid core made up of motor neuron cell bodies: “gray matter”

• 31 pairs of spinal nerves branch out to the body

• Spinal Reflexes: these don’t go to the brain, instead they go to the spinal cord—– Ex. patellar reflex

Reflexes

• An automatic reaction to some sense message, like pain– Don’t need to think or make decisions about

something

• The information gets processed in your spinal cord– Your muscles begin to react immediately even

before your brain gets the news of what’s happening.

– This is called a reflex arc

Reflex Arc

• Begins at a receptor– Sensory neurons in the skin receive a

stimulus

• Travels to the reflex center (spinal cord)

• Ends at an effector– A muscle or gland that reacts to the stimulus

Reflex Arc

A pathway of nerve impulses1. Stimulus – a change in the environment that causes

a change in the body2. Receptor – specialized organ that receives the

stimulus3. Sensory neuron – brings the stimulus to the spinal

cord4. Synapse – space between neurons5. Interneuron – neurons in the spinal cord6. Motor neuron – brings the stimulus from the spinal

cord to the correct part of the body7. Effector – muscle or gland that reacts to the

stimulus

The Patellar Reflex

Peripheral Nervous System(Motor and Sensory)

Motor Division: signals away from CNS• Somatic nervous system is for voluntary

muscle control. These neurons control the skeletal muscles….

• Autonomic nervous system is automatic or involuntary– Control of heart rate, respiration, blood

pressure, smooth muscle, etc. – This has 2 separate divisions: sympathetic

and parasympathetic

Autonomic: Sympathetic Division & Parasympathetic Division

• Sympathetic: Shunting of blood from one part of body (ex = stomach to heart) to another. Activated by physical or emotional stress. “Fight or Flight” response.

• Parasympathetic: Routine life, conserves energy, heart rate lowers, digestive organs back to normal. “Rest and Ruminate” response.

Autonomic NS: Parasympathetic and Sympathetic Controls

Peripheral Nervous SystemSensory Division

• Sensory neurons carry messages toward the CNS from sensory receptors all over body.

• Sensory receptors act as “energy transducers.” A transducer is a device for converting a non-electrical signal into an electrical one. In this case, the electrical signal produced is the action potential of a nerve.

• Sensory receptors are in sense organs, such as eyes, ears, mouth, nose, skin… and different regions of the brain respond to different signals.

Types of Sensory Receptors

Stimulus Type of Sensory Receptor

Location

Light Photoreceptors Retina

Mechanical Mechanoreceptors Under the skin, inner ear

Heat Thermoreceptors Hypothalamus, under the skin

Pressure Baroreceptors Walls of some arteries

Chemicals Chemoreceptor Mouth, nose

Transmission of neural signals: How it Works…

• In general, the signaling activity of the nervous system is composed of electrical activity within neurons and chemical flow between neurons. Quite a complex network!

• 200 years ago… found out that a recently dead animal will still contract muscles if an electrical stimulation is sent through.

Parts of the Brain

• Cerebrum– Largest and most prominent– Responsible for voluntary or conscious activities of

the body– Site of intelligence, learning and judgment– Divided into left and right hemispheres, which deal

with opposite sides of the body– Folds and grooves on surface increase surface area– Two layered

• Cerebral cortex – outer layer – gray matter – cell bodies– Processes information from the sense organs and controls

body movements• Inner layer – white matter – axons w/myelin sheaths

Parts of the Brain• Cerebellum

– Located at the back of the skull– Coordinates and balances the actions of the muscles

• Brain Stem– Connects brain and spinal cord– Includes two regions, pons and medulla oblongata

• Regulates the flow of information b/w the brain and the rest of the body.

• Some important body functions (heart rate, swallowing, breathing) are controlled here

Parts of the Brain

• Thalamus & Hypothalamus– b/w brain stem and cerebrum

• Thalamus– Receives messages from sensory receptors and then

relays to cerebrum

• Hypothalamus– Control center for recognition and analysis of hunger,

thirst, fatigue, anger and temp.– Controls coordination of nervous and endocrine

systems

The Endocrine System

Endocrine System

• A set of glands that produce hormones-- chemical messengers that circulate in the blood

Hormone• Chemical messengers produced by

the endocrine glands and circulated in the blood

• Similar to neurotransmitters in that they are also messengers

• Slower communication system, but with longer lasting effects

Endocrine System

Hypothalamus

• Brain region that controls the pituitary gland

• Controls homeostasis – the bodies ability to remain at a status quo level

Pituitary Gland• The endocrine system’s gland that controls the other

endocrine glands• Called the “master gland”• Located at the base of the brain and connects to the

hypothalamus• Controls thirst by controlling the amount of water in

the body’s cells• Controls female contractions, and tells the mammary

glands to produce milk for newborns• May control grooming habits, companionship, and

sexual behavior• Controls the flow of the human growth hormones –

dwarfism and gigantism

Thyroid Gland

• Endocrine gland that helps regulate the energy level in the body

• Located in the neck• controls body temperature • Controls metabolism – our body’s ability to

transform the food we eat into usable energy• Overactive- Behaviors may include excitability,

insomnia, ADD, agitation, difficulty focusing• Reduced Activity- Behaviors may include

sleepiness, reduced muscle tone, overweight

Adrenal Gland

• Endocrine glands that help to arouse the body in times of stress

• Located just above the kidneys• Release epinephrine (adrenaline)

and norepinephrine (noradrenaline)

• Increase heart rate, blood pressure, and blood sugar

Pancreatic Gland

• Regulates the level of blood sugar (insulin) in the blood

• Insulin is needed in the body to break down sugars in the body

• Too much insulin in the body devours all of the sugar in the blood. Behaviors exhibited include sluggishness and inattentiveness.

• Too little insulin causes a buildup of sugar in the blood and makes the kidneys use a lot more water to flush it out of the body. The extra water needed to flush the sugar comes from surrounding cells, which in turn dehydrates them and leaves them vulnerable to infection and poisons.

Sex Glands

• Ovaries (females) and testes (males) are the glands that influence emotion and physical development.

• Testosterone – primary male hormone• Estrogen – primary female hormone• Males and females have both estrogen

and testosterone in their systems.

Gonads

• Testicles – release androgens (male hormones)

• Ovaries – release estrogens (female hormones)

• The presence of these chemicals influence male and female reproductive characteristics.

Maintaining Homeostasis

• Homeostasis is the maintenance of a stable internal state within an organism.

• Organisms detect changes in their environment and respond to these changes in a variety of ways. 

• A feedback mechanism occurs when the level of one substance influences the level of another substance or activity of another organ.

Feedback Mechanisms

Three parts of the mechanism– Sensor – something that can detect a change

• Ex. Structures in the brain detect change in CO2 levels

– Control Unit – something that knows what the correct level should be

• Ex. Information in the brain is preset for the correct CO2 level

– Effector – something to take the instructions and make changes

• Ex. Muscles in the chest used for breathing

Feedback Mechanisms

• Positive feedback - designed to accelerate or enhance the output created by a stimulus that has already been activated.

• Designed to push levels out of normal ranges.

• Example is the release of oxytocin to intensify the contractions that take place during childbirth. – The more oxytocin, the greater and more frequent the

contractions, which in turn produces more oxytocin

Feedback Mechanisms

• Negative feedback – process in which a stimulus produces a response that opposes the original stimulus.

• Ex. Blood sugar regulation– An increase in blood sugar level triggers the release of the hormone

insulin by the pancreas– the hormone insulin lowers blood sugar level restoring the body to its

original blood glucose level in two major ways:• it increases the ability of body cells to take in glucose from the blood • it converts blood glucose to the compound glycogen -- this compound is

also called animal starch and is stored in our liver and muscles

– A decrease in blood sugar levels triggers the release of the hormone glucagon by the pancreas

• It causes the liver to release glucose into the blood to regulate blood sugar levels

Regulation Disorders

• Nervous System– Cerebral Palsy – affect the ability to control body

movements– Alzheimer’s – progressive degenerative disease;

lose memory and ability to think, speak, etc.– Multiple Sclerosis – cells in the brain and spinal

cord do not function normally.• Wide variety of symptoms

Regulation Disorders

• Endocrine System– Diabetes – interruption of the feedback

system that controls blood sugar.– Type I – born with it

• Controlled by insulin injections

– Type II – acquired• Usually occurs in older people• May be controlled with diet