The Nervous System

1
The Nervous System

• Biology 12
• Ms. Bowie

2
Divisions on the Nervous System
3
The Central Nervous System (CNS)
4
The Peripheral Nervous System (PNS)
5
Parasympathetic vs Sympathetic
6
Anatomy of a Nerve Cell
7
Anatomy of a Nerve Cell

• Dendrites carry impulses toward the cell body.
• Axon are extensions of cytoplasm that carries
  nerve impulses away from the cell body.
• Myelin sheath is the insulated covering over the
  axon of a nerve cell. Myelin is formed by special
  cells known as Schwann cells.
• Nodes of Ranvier are the gaps between the
  sections of myelin sheath. Impulses can jump from
  node to node, speeding transmission.

8
Neuron Terminology

• Glial cells are non-conducting that provide
  support and metabolism for the nerve cells.
• Sensory neurons carry impulses from sensory
  receptors to the CNS also known as afferent
  neurons.
• Ganglia are clusters of sensory neurons outside
  the CNS

9
Neuron Terminology

• Motor neurons carry impulses from CNS to the
  effector cells (muscles, organs and glands) to
  produce a response also known as efferent
  neurons.
• Interneurons are neurons that act as links
  between the sensory and motor neurons. They
  generally make up the CNS. They interpret the
  sensory info and stimulate the motor neurons.

10
Neuron Terminology

• Neurilemma is a delicate membrane that surrounds
  the axon of some nerve cells
• its promotes the regeneration of the axon when
  damaged.
• found mostly in the PNS.
• explains why feeling eventually returns to you
  skin after a paper cut.

11
Reflex Arcs

• Very strong, damaging stimulus can cause a reflex
  reaction that does not involve the message being
  sent up to the brain.

12
Check your understanding

1. Describe the difference between the CNS and the
   PNS.
2. Differentiate between sensory nerves and motor
   nerves.
3. Describe the function of dendrites, myelin
   sheath, Schwann cells, cell body and axon.
4. Name the 5 essential parts of the reflex arc.
5. Describe the process of a reflex reaction.

13
The Central Nervous System in Detail

• The brain is surrounded by tough three-layer
  protective membrane known as the meninges. There
  are 3 layers
• Dura mater outer layer
• Arachnoid mater middle layer
• Pia mater inner layer
• The meninges form the blood-brain barrier. This
  barrier determines what chemicals will reach the
  brain.
• The brain and spinal cord float in a liquid known
  as the cerebrospinal fluid.

14
The Spinal Cord

• The spinal cord carries doral sensory nerve
  messages from receptors to the brain and ventral
  motor nerve messages from the brain to the
  muscles, organs glands.
• There are 2 types of nerve tissue in the cord
  grey matter and white matter. White matter
  contains myelinated neurons (sensory and motor
  neurons). Grey matter is made of interneurons.

15
The Brain Three Distinct Regions

• Forebrain
• Olfactory lobes (smell)
• Cerebrum
• Coordinates sensory motor function
• Speech, reasoning, memory and personality
• Divides into 4 lobes frontal, parietal,
  occipital, temporal
• Thalamus, hypothalamus the pituitary gland
• Cerebral cortex
• Grey matter
• Contains folds that increase the surface area
• Deep folds are known as fissures
• The corpus callosum is a bundle of nerves that
  connects the two hemispheres of the cortex.

16
The Brain Three Distinct Regions

• Midbrain
• involved in the motor functions
• vision, basic movements, and hearing.
• An area called the substantia nigra plays a role
  in releasing dopamine-producing neurons
• Because the midbrain is involved in muscle
  movement, the death of neural cells in the
  substantia nigra can lead to Parkinson's disease

17
The Brain Three Distinct Regions

• Hindbrain
• Pons
• The pons a bridge region
• The pons also helps regulate breathing.
• Medulla oblongata
• The last three centimeters of the brain stem.
• Responsible for regulating our bodies heart rate,
  respiration, and blood pressure.
• Cerebellum
• The cerebellum is the second largest structure in
  the brain
• Receives sensory input from a tendon, muscle, and
  joint receptors.
• Needed for motor learning as well as movement
  muscle tone.

18
The Brain The Cerebrum

• 4 lobes
• Frontal lobe
• Parietal lobe
• Temporal lobe
• Occipital lobe

19
The Frontal Lobe

• Handles the complex thoughts.
• Involved in planning, organizing, problem solving
  and selective attention.
• The front portion is called the prefrontal
  cortex.
• It controls "higher cognitive functions"
  including behavior and emotions and the
  determination of the personality.
• The back holds the motor areas that produce
  movement.
• The frontal lobe is divided from the parietal
  lobe by the central sulcus.

20
The Parietal Lobe

• The parietal lobes controls sensation like touch
  or pressure.
• Behind the primary sensory cortex is a large
  association area that controls fine sensation
  which are judgment of texture, weight, size or
  shape.

21
The Occipital Lobe

• Occipital Lobe processes visual information.
• Damage to this lobe can cause visual deficits.

22
The Temporal Lobe

• These lobes allow a person to tell one smell from
  another and one sound from another.
• They also help in sorting new information and are
  responsible for short-term memory.
• Right Lobe involved mainly in visual memory  like
  pictures and faces while left lobe involved
  mainly in verbal memory  such as words and names.

23
Check your understanding

1. List the four regions of the cerebral cortex and
   state the function of each.
2. If a physician cuts the corpus callosum how might
   this affect the patient?
3. Name the meninges and explain what they do.
4. If you wanted to learn more about how memories
   form and are stored, what area of the brain would
   you study?

24
Homeostasis The Autonomic Nervous System

• The autonomic nervous system is part of the PNS.
• It works with the endocrine system to help the
  body adjust to changes in the external and
  internal environment.
• They are all motor nerves that regulate the
  organs of the body without conscious control.
• Made of 2 parts
• The sympathetic and parasympathetic nervous
  systems.

25
Homeostasis The Autonomic Nervous System
Organ Sympathetic (prepares for stress) Parasympathetic (restores normal balance)
Heart Increases heart rate Decreases heart rate
Digestive Decreases peristalsis Increases peristalsis
Liver Increases the release of glucose Stores glucose
Eyes Dilates pupils Constricts pupils
Bladder Relaxes sphincter Contracts sphincter
Skin Increases blood flow Decreases blood flow
Adrenal gland Causes release of epinephrine No effect