What does your nervous system do for you?

The nervous system is responsible for regulating your body temperature, sending signals to the brain through nerves, and controls movement. It is the master control and communication system of our body.

Parts of the Nervous System

Brain, Spinal Cord, Nerves, Sensory Organs(5 senses)

Functions of the Nervous System

Sensory Input, Integration, Motor Output

Sensory Input

Stimuli; noticing things

Integration

Process of carrying out information by your CNS; translating what you notice

Motor Output

Muscle/Gland; Using bodily movements to control movement

Central Nervous System (CNS)

\-Made up of the brain and spinal cord

\-Acts as the body’s control center and coordinates bodily activities

\-Acts as the integration and command center

How does the CNS act as the body’s control center?

Impulses travel through the neurons in your body to reach the brain

What is the primary function of CNS?

* Takes in conscious and unconscious thoughts 
* Makes decision for controlling and maintaining homeostasis
* Asks as integration as a command center

Peripheral Nervous System (PNS)

* Made up of everything else (nerves/nerve endings) that carry messages to and from the CNS 


* Carries Impulses to and from CNS to glands and muscles
* Links all parts of the body by carrying impulses from the sensory receptors to the CNS and from the CNS to glands or muscles

What are the two main parts of the PNS?

Somatic Nervous System & Autonomic Nervous System

Somatic Nervous System

* Relay info between the skin, skeletal muscles and CNS
* You consciously control this pathway by deciding whether or not to move muscles (except reflexes)

Autonomic Nervous System

\-Relay info from CNS to organs

Reflexes

automatic response to stimuli

Involuntary

You do not consciously control these

Sympathetic Nervous System

control in times of stress such as flight or fight

Parasympathetic Nervous System

* controls body in times of rest

Sensory Division (AFFERENT)

The division of the PNS composed of nerves that carry information **TO** the CNS

Motor Division (EFFERENT)

The division of the PNS composed of nerves that carry information **FROM** the CNS

Neurons

Nerve cells

Dendrites

Fibers that receive and convey messages to the cell body of a neuron

Cell Body

Metabolic center of the cell; contains the nucleus

What are the two cell types?

Support Cells aka neuroglia and neurons

What is the job of the Supporting Cells/Neuroglia?

To insulate, support, and protect delicate neurons

Axon Terminal

* At their terminal end axons branch into hundreds or thousands of axon terminals
* Each contains vesicles or sacs of neurotransmitters
* When a nerve impulse reaches an axon terminal it stimulates the release of neurotransmitters

Synapse

The junction between neurons

What are synapses used for?

* Neurotransmitters diffuse across the synapse to continue cell to cell communication

Tracts

Bundles of nerve fibers in CNS

White Matter: Myelinated Axons

Grey Matter: Unmyelinated Cell Bodies

How are neurons classified?

* Sensory Neurons, Interneurons, Motor neurons

Sensory Neurons

* carry impulses from receptors such as the skin to the CNS

Interneurons

connect sensory and motor neurons in the CNS

Motor Neurons

carry impulses from the CNS to a muscle or gland

Proprioceptors

* Sensory receptors in the muscles and tendons
* Detect stretch or tension in skeletal muscles, tendons and joints
* Maintain balance and posture

Four Types of Neuron Structure

Unipolar, Bipolar, Multipolar(most common), Pseudounipolar

Two major functional properties of neurons

Irritability & Conductivity

Irritability

Ability to respond to a stimulus and convert it into a nerve impulse

Conductivity

Ability to transmit the impulse to other neurons, muscles, or glands

Things that excite a neuron

Lights, sound waves, pressure, chemicals, neurotransmitters

Events in a Nerve Impulse

1. Neuron at rest is polarized
2. Stimulus changes membrane permeability
3. Depolarization & generation of action potential
4. Action potential propagates along entire length of neuron
5. Repolarization-membrane returns to resting state
6. Sodium-potassium pump restores ion balance

Neurotransmitters

* Chemicals released at the end of an axon terminal that diffuse across the synapse and transfer the nerve impulse to another nerve, muscle, or gland

How do neurons communicate?

Via electrical and chemical synapses

4 Major Brain Regions

Cerebrum, Diencephalon, Brain Stem, Cerebellum

Cerebrum

* The largest and most superior part of the brain
* Composed of 2 cerebral hemispheres divided by longitudinal fissure
* Surface shows elevated ridges of tissues called gyri and shallow grooves called sulci

Cerebral Cortex

* Outermost layer of the cerebrum
* Composed of gray matter
* Responsible for thinking and processing information from the five senses

Cerebral Lobes

* Grooves or fissures divide into sections or lobes

Frontal Lobe

* Motor function, problem solving, memory, language, judgment, socially acceptable behavior

Parietal Lobe

* Processes sensory information such as touch, temperature, and taste

Temporal Lobe

* Auditory perception, Olfactory area is deep inside

Occipital Lobe

Visual processing center

Diencephalon

* Superior to the brainstem
* 3 major structures: Thalamus, Hypothalamus, Epithalamus

Thalamus

* Relay station for sensory impulses traveling to the sensory cortex

Epithalamus

* Contains the pineal gland and choroid plexus which forms the cerebrospinal fluid

Hypothalamus

Keeps your body in homeostasis

Brain Stem

Made up of the midbrain, pons, and medulla oblongata

Midbrain

* Reflex center for vision and hearing, eye movements

Pons

Coordinates information between brain areas, involved in breathing

Medulla Oblongata

* Blood pressure, breathing, heart rate

Cerebellum

* Precise timing of skeletal muscle activity
* Balance and equilibrium
* Makes body movement smooth and coordinated

Bones

Skull and vertebrae

Meninges

Connective tissue matter

Dura Mater

Tough outer double layer membrane

Arachnoid Mater

Web-like layer spans the subarachnoid space

Pia Mater

Innermost membrane that clings tightly to the surface of the brain and spinal cord

Cerebrospinal Fluid (CSF)

* Continually formed plasma by clusters of capillaries in cavities called ventricles
* Provides a watery cushion for the brain & spinal cord
* Significant changes in CSF composition may indicate problems

How is CSF obtained for testing?

It’s obtained through a procedure called a spinal or lumbar tap

Blood Brain Barrier

* The brain depends on a very stable internal environment
* Neurons are protected from blood-borne substances by the least permeable capillaries in the body

Spinal Cord

* Continuous with the brain stem; connects the brain to nerves
* Enclosed within vertebrae; provides a 2-way path to and from the brain
* Major reflex center

Peripheral Nervous System (PNS)

Endoneurium, Perineurium, Epineurium

Endoneurium

Surrounds each neutron

Perineurium

Surrounds a group of neurons or fascicle

Epineurium

Surrounds a nerve

How many pairs of spinal nerves are there?

* 31 pairs of spinal nerves exit from the vertebral column

Plexus

* All other spinal nerves form complex networks each called a plexus, which serve the motor and sensory needs of limbs

Cranial Nerves

Nerves that originate in the brain

How many pairs of cranial nerves are there?

12 pairs that serve the head and neck

Autonomic Nervous System

* Motor subdivision of the PNS that automatically controls bodily activities
* Maintains homeostasis
* Includes neurons that control cardiac muscle, smooth muscle, glands

Fight or Flight

* The sympathetic nervous system prepares the body to either fight or run from a threat
* Enables the body to cope rapidly and vigorously with situations that may disrupt homeostasis

Parkinson’s Disease

* A motor system disorder that leads to trembling of the hands, arms, legs, jaws, or face and impaired balance and coordination
* Results from a loss of brain cells in area of the midbrain called the substantia nigra

Multiple Sclerosis

Occurs when the Myelin Sheath around neurons is gradually destroyed and hardens into “scleroses”

Nerve impulse are interrupted

Autoimmune disease with no cure

Alzheimer’s

A type of mental illness caused by progressive brain cell death

Leads to problems with memory, thinking, and behavior

Symptoms worsen over time and there was no cure

Concussion

A mild traumatic brain injury

Caused by a jolt, bump, or blow to the head that causes the brain to move rapidly inside the skull

Symptoms: Dizziness, confusion, headache & nausea

Meningitis

Acute inflammation of the meninges

Usually caused by vital or bacterial infection

Can lead to deafness, epilepsy, brain damage, or death

Symptoms: sever headaches & neck stiffness

Epilepsy

Brain disorder that causes seizures

Stroke

Occurs when something blocks oxygen supply to the brain and a blood vessel bursts