NERVOUS SYSTEM

• complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body

• considered as the body’s storage center of information and also the body’s control system

• mainly responsible for controlling and coordinating all the organ systems by sending messages from the brain through nerve signals

• makes sure that all the parts of the body are working together efficiently

MAJOR DIVISIONS AND PARTS OF THE NERVOUS SYSTEM

CENTRAL NERVOUS SYSTEM

• consists of brain and spinal cord

• receives and sorts out information and determines the appropriate action

• CNS is like a CPU of a computer

• has 12 pairs of cranial nerves (brain)

• 31 pairs of spinal nerves (spinal cord)

• acts as the body’s control center and coordinates body’s activities

• main processing center of the nervous system

• has two components: brain and spinal cord

BRAIN

• organ located within the skull that functions as organizer and distributor of information for the body

• has three main parts:

  • Cerebrum – large, upper part of the brain that controls activity and thought

  • Cerebellum – part under the cerebrum that controls posture, balance, and coordination

  • Brainstem – connects the brain to the spinal cord and controls automatic functions such as breathing, digestion, heart rate, and blood pressure

SPINAL CORD

• channel for signal between the brain and the majority of the body parts

• controls some simple musculoskeletal reflexes even without the processing of the brain

PERIPHERAL NERVOUS SYSTEM

• made up of nerves

• through these nerve cells, communication between the CNS and the body tissues take place

• made up of all the nerves that carry messages to and from the central nervous system

• CNS and PNS work together to make rapid changes in your body in response to stimuli

• connects the central nervous system to the organs and limbs

• has two main divisions: somatic nervous system and autonomic nervous system

SOMATIC NERVOUS SYSTEM

• associated with the voluntary control of body movements

• relay information between skin, skeletal muscles and CNS

• soma means body

• has two main parts:

  • Spinal Nerves – carry motor and sensory signals between the spinal cord and the body

  • Cranial Nerves – nerve fibers that carry information into and out of the brainstem

AUTONOMIC NERVOUS SYSTEM

• associated with the involuntary control of body movements

• communicates with smooth muscles, heart muscle, and glands

• relay information from central nervous system to organs

• involuntary: you do not consciously control these

• two groups of nerves

  • important both to maintain homeostasis

• has two subdivisions:

  • Sympathetic Nervous System

    • activated when the body is in a dynamic role or stress (e.g., increased heart rate and breathing, dilation of pupil, sweating)

    • speed upon slow down some body processing

    • seems calming but not

    • stress

    • increased heartbeat

    • “fight or flight”

  • Parasympathetic Nervous System

    • maintains body functions and restores the body to normal or relaxed mode

    • have the opposite effect on the same body processes

    • relax

    • slow heartbeat

    • “rest and digest”

BRAIN

CEREBRUM (FOREBRAIN)

• 2 hemispheres

• integration

• billions of neurons and synapses

• controls memory, intelligence, muscles

• controls conscious activities, intelligence, memory, language and muscles

• cerebral cortex – part of the cerebrum that is wrinkled with countless folds and grooves

• largest part of the brain

• outer: grey matter = cell bodies

• middle: white matter = nerve fibers

• inner: neurons

• divided into four lobes

  • Frontal Lobe – executive, speech

  • Parietal Lobe – sensations, sensory information, speech, taste

  • Occipital Lobe – vision, visual association

  • Temporal Lobe – language, memory, hearing, smell association area

CEREBELLUM (HINDBRAIN)

• controls balance, posture, and coordination

• muscle coordination is developed here as well as the memory of physical skills

• if the cerebellum is injured, your movements become jerky

• body control, motion memory

BRAINSTEM

• controls involuntary activities such as breathing, circulation, digestion

• made up of the medulla oblongata, pons and midbrain

  • Medulla Oblongata – controls involuntary activities such as heart rate and breathing

  • Pons and Midbrain – acts as pathways connecting various parts of the brain with each other

  • Midbrain – eye movements and size of the pupils, coordinates movement with sight and sound

• sometimes called the reptilian brain, as it resembles the entire brain of a reptile

CORPUS CALLOSUM

• connection of nerves between the two hemispheres

BASAL GANGLIA

• group of structures near the center of the brain

• manages the signals that the brain sends to move muscles

• for motor control, motor learning, executive functions, behaviors and emotions

THALAMUS

• sorts data

HYPOTHALAMUS

• homeostasis

POSTERIOR PITUITARY

• hormones

SOMATOSENSORY CORTEX

• located in the parietal lobe

• receives sensory information

• input

MOTOR CORTEX

• generates signals to direct the movement of the body

• output

THE NERVE CELL

• Neuron or nerve cell – basic unit of structure and function in the nervous system

• cells that conduct impulses

• made up of dendrites, cell body, and an axon

• has a cell body containing the nucleus

• in the cell body there are root-like structures called the dendrites and axons

• Dendrites

  • carry impulses toward the cell body

  • branch-like extensions that receive impulses

• Axons

  • carry impulses away from the cell body

  • single extension of the neuron

• the axon branches out at ending to send impulses to many different neurons

• dendrites receive impulses from many other axons

• Synapse – gap between neurons

• the ends of an axon do not touch the dendrites of another neuron

• there is a very tiny space between them across which a message is transmitted, this space is called synapse

3 TYPES OF NEURONS

• Sensory Neurons

  • carry impulses from inside and outside the body to brain and spinal cord

• Interneurons

  • found within brain and spinal cord, process incoming impulses and pass them on to motor neurons

• Motor Neurons

  • carry impulses away from the brain and spinal cord

SO HOW DO THESE NEURONS WORK IF SOMEONE TAPS YOU ON THE SHOULDER?

1. Receptors in the skin sense touch or other stimuli.

2. Sensory neurons transmit the touch message.

3. Information is sorted and interpreted in the brain. A response is determined by interneurons.

4. Motor neurons transmit a response message to the shoulder muscles.

5. The shoulder muscles are activated, causing the head to turn.

NERVE IMPULSE

• small electric charge

• nervous system carries signals throughout the body in the form of nerve impulses

MYELIN SHEATH

• a sleeve that’s wrapped around each cell (neurons)

• protective layer of fat (lipids) and protein that coats the main “body” section of a neuron called the axon

NODES OF RANVIER

• microscopic gaps found within myelinated axons

• speed up propagation of action potentials along the axon via saltatory conduction

HOW IS AN IMPULSE TRANSMITTED?

1. Stimulus excites sensory neurons.

2. Depolarization (a change in charge due to sodium ions) creates a wave of changing charges down the axon.

3. Impulse moves across the synapse (tiny space between one neuron’s axon and another’s dendrites) with the help of neurotransmitters.

HOW ARE NERVE IMPULSES TRANSMITTED?

1. Signal of the message is picked up by the dendrites of the neuron.

2. Message travels along the neuron.

3. When the nerve impulse reaches the end of the axon, it triggers the knobs on them.

4. The knobs release a chemical called a neurotransmitter.

5. The chemical passes across the synapses to reach the dendrites of the next neuron.

6. The nerve impulse will travel along this neuron, pass across the synapse to the next neuron and go on.

REFLEX ARC

REFLEX ACTION

• information coming from the senses and provide motor responses that do not come from the brain

WAYS TO FIND COMPLICATIONS IN NEURONS/BRAIN

• Electroencephalogram (EEG)

• Magnetic Resonance Imaging (MRI)

• Computerized Axial Tomography (CAT)

NERVOUS SYSTEM DISEASES AND DISORDERS

• Alzheimer’s Disease

• Epilepsy

• Multiple Sclerosis

17 STRUCTURES OF THE BRAIN

1. Brainstem

2. Medulla Oblongata

3. Pons

4. Midbrain

5. Cerebellum

6. Thalamus

7. Hypothalamus & Posterior Pituitary

8. Cerebrum

9. Corpus Callosum

10. Basal Ganglia

11. Cerebral Cortex

12. Frontal Lobe

13. Parietal Lobe

14. Occipital Lobe

15. Temporal Lobe

16. Motor Cortex

17. Somatosensory Cortex