nervous system and endocrine system

Nervous system

It starts with an individual nerve cell called a neuron.

Neurotransmitters - Chemicals held in terminal buttons that travel through the synaptic gap

Cell body - the cell’s life support center

Dendrites - receive messages from other cells

Axon - passes messages away from the cell body to other neurons, muscles, or glands

Myelin sheath - covers the axon of some neurons and helps speed neural impulses

  • Multiple sclerosis - Myelin sheath destroyed

Terminal branches of axon - from junctions with other cells

How does a neuron fire

Resting potential - when a neuron is resting but ready to fire or generate an action potential

If enough of a neurotransmitter pushes a neuron past its threshold, then…

An Action Potential or neural impulse is created and the neuron fires

All - or - none response - neurons fire or they

don’t and always with the same intensity

Types of neurotransmitters

  • Acetylcholine (ACh)

    • Too much and you will be depressed or anxious

    • Too little and you will possibly get Alzheimer’s Disease

  • Dopamine

    • Deals with motor movement, learning, attention, and emotion

    • Not enough - Parkinson’s Disease

    • Too much - Schizophrenia

  • Serotonin

    • Involved in hunger, sleep, and mood control

    • Lack of serotonin - depression

    • Too much - Serotonin syndrome

      • life-threatening

      • mental confusion

      • disorientation

  • Endorphins

    • Relieve pain and elevate mood

    • They are our body’s natural opiates

    • Many of our most addictive drugs deal with endorphins or street drugs that mimic endorphins

Drugs can be

  • Agonists - mimic certain neurotransmitter’s effects (increase an effect/help the neurons fire)

  • Antagonists - stop neural firing. (decrease an effect or amount of neurotransmitters)

The neural train

Receptor cells - Cells one very sensory system that responds to sensory stimuli and sends nerve impulses along sensory neurons

Sensory neurons - take information from the sensory receptor cells to the brain

Interneurons - nerve cells in the brain and spinal cord that process information

Motor neurons - take information from the brain to the muscles and glands

Reflexes - when a reflex occurs the signal only reaches the spinal cord and never reaches the brain (automatic response: No thinking required)

Central nervous system - The brain and spinal cord.

  • The spinal cord is sometimes called your “back” or spinal column

Peripheral nervous system

  • All nerves that are not encased in bone

  • Branch off of the spinal cord

  • Is divided into two categories, somatic and autonomic

Somatic nervous system

  • Controls voluntary muscle movement

  • Uses motor neurons

Autonomic nervous system

  • Control the automatic functions of the body

  • divided into two categories, the sympathetic and the parasympathetic

Sympathetic nervous system

  • Redies us for the “Fight or flight” response

  • Automatically accelerates heart rate, and breathing, dilates pupils, slows down digestion

Parasympathetic nervous system

  • Automatically slows the body down after a stressful event (calming)

  • Heart rate and breathing slow down, pupils constrict and digestion calms down

The endocrine system

Similar to the nervous system, except hormones work a lot slower than neurotransmitters because they travel through the bloodstream

Endocrine system

  • System of glands that secrete hormones

  • Controlled by the hypothalamus

Hypothalamus

  • Part of the grain and attached to the pituitary

  • Controls pituitary gland

Pituitary gland

  • “Master Gland”

    • Controls the other endocrine glands

  • Growth Hormone (GH)

    • Too much - Gigantism

    • Too little - Dwarfism

  • Anti - diuretic (ADH)

    • Stimulates kidneys to keep water

Thyroid gland

  • Regulates:

    • Metabolism and energy balance

    • Hyperthyroidism - too much thyroid hormone: excessive energy, hyper, weight loss

    • Hypothyroidism - Not enough thyroid hormone: tired, no energy, weight gain, hair loss, cold

Adrenal gland

  • Releases adrenaline to deal with stress or an emergency

  • Adrenaline is also called epinephrine

Male and female sex glands

  • Ovaries and testes

  • The primary male hormone is testosterone

  • The primary female hormone is estrogen

  • Regulate the development of sex organs and secondary sex characteristics

Pancreas

  • Secretes insulin

  • Hypoglycemia: Low blood sugar >70

  • Hyperglycemia: High blood sugar >100