The Nervous SystemThe Nervous System

Neuron – working unit of the nervous system

Axon – carries messages away from the cell body

dendrites – receive the messages and send them to the cell body

Terminal Bud – send messages to other neurons

3 types of neurons

• Sensory neurons – send info to the spinal cord or brain

• Interneurons – send info out of brain and spinal cords to the motor neurons

• Motor neurons – send info from brain and spinal cord to muscles or glands

Sensory neuron (hand)

Motor neuron

(arm)

Interneuron

Synapse

• Small space in between neurons

• Neurotransmitters are released in the synapse and starts an impulse in the next neuron

Synapse

Divisions of the Nervous System

CNS – central nervous system – brain and spinal cord

PNS – peripheral nervous system – all the nerves outside the CNS

Central Nervous System

• Brain 100 billion neurons

• 3 major parts

1. Cerebrum

• Divided into hemispheres

• Memory is stored

Cerebrum

2. Cerebellum

• Under the cerebrum

• Coordinated voluntary muscle movements

3. Brainstem

• Connects the brain to the spinal cord

• Made up of the – Mid brain– Pons– Medulla

• Controls homeostasis of heart, breathing, blood pressure, involuntary muscle movements

Peripheral Nervous System

• 2 divisions of the peripheral nervous system

Peripheral

Nervous System

Somatic

Nervous System

Skeletal Muscle

Autonomic

Nervous System

Heartrate, breathing, digestion, salivary glands

Reflex

• Involuntary response to a stimulus

• Involves a pathway called a (reflex arc) over which impulses travel

Reflex arc

1. Impulse is sent to the spinal cord

2. Impulse passes to an interneuron in the spinal cord which immediately relays the impulse to motor neurons

3. Motor neurons transmit the impulse to muscles in your arm

4. Your arm pulls back (Without thinking!)

Steps of a reflex arc1. Receptor

2. Sensory neuron

3. Interneuron (spinal cord)

4. Motor neuron

5. Effector – “response”

Your Endocrine System

Endocrine system

• System of glands that release their products into the blood stream and broadcast messages throughout the body

Hormones

• Affect specific tissues called target cells

Target cells – control activities in parts of the body other than right around the gland

Glands of the Endocrine System

Hypothalamus• Part of the brain

• Produces hormones that influence the pituitary gland

Pituitary Gland• “Master Gland”

• Secretes numerous hormones

• Growth-stimulating Hormone

• Hormones to control specific glands

• Thyroid Stimulating Hormone (TSH)– Tells thyroid to produce thyroxine

• The Follicle Stimulating Hormone– Stimulates activity in the ovary and testes

Thyroid Gland• Located in the neck

• Makes thyroxine

• Regulates metabolism

Parathyroid Glands• Embedded in the thyroid gland• Secrete parathormone• Controls the metabolism of calcium• Necessary for nerve function,

blood clotting, and proper growth of teeth and bones

Adrenal Glands• Two glands located on top of the

kidneys

• Each gland has 2 distinct regions

Adrenal Cortex• Secretes two types of steroid hormones

1. promotes the conversion of body fat and protein into glucose

2. promotes the reabsorbtion into the blood stream of sodium and chloride ions by the kidney tubules

– This affects the water balance and maintains BP

Adrenal Medulla• Secretes adrenalin in times of

emergency

• Increases the blood sugar level

• Speeds heart and breathing rates

Islets of Langerhans• Located in the pancreas

• Secrete insulin and glucagon

Insulin• Helps take glucose into cells

• Lowers blood sugar levels by taking it out of the blood and storing it in the liver and muscle cells

Glucagon• Stimulates the release of sugar

from the liver

• Raises blood sugar level

Gonads• Sex glands• Testes • Secrete testosterone – develop male

secondary sex characteristics• Ovaries• Secrete estrogen - develop female

secondary sex characteristics

Endocrine Control• Negative feedback system

• Controls the amount of hormone an endocrine gland produces

• Works like a thermostat in your house

Negative feedback system

Start: 1. Hormone level low

2. Hormone production increases

3. Hormone level high

4. Hormone production slowed down

End: 5. Hormone level low

Endocrine Feedback System of TSH

Hypothalamus

Pituitary Gland

Thyroid

Stimulating

Hormone

Thyroid Gland

Thyroxin

stimulates

Inhibits

Endocrine System Disorders

Goiter• Enlargement of the thyroid gland

• Results in not being able to make thyroxine

• Often associated with iodine deficiency in the diet

Diabetes• Insulin deficiency

• Results in an elevated blood sugar level

• Also an inability of the body to store the sugar glycogen in the liver