Nervous System Organization

List all the Glial Cells?

Support cells of the nervous system with many functions.

1. Astrocytes:

2. Microglia:

3. Ependymal Cells

4. Oligodendrocytes (CNS)

5. Schwann Cells (PNS)

6. Radial

What are Astrocytes? (Glial Cell)

1. Astrocytes:

   • Form the blood-brain barrier

   • Regulate extracellular fluids

(CNS)

What are Microglia?

1. Microglia:

   • Protect the nervous system

   • Scavenge dead cells and pathogens

(CNS)

What are Ependymal Cells?

1. Ependymal Cells:

   • Line fluid-filled cavities (ventricles)

   • Help produce cerebrospinal fluid (CSF)

(CNS)

What are Radial Gila?

They form track sin developing embryo.

Newly formed neurons migrate from the neural tube along the tracks made by radial glia.

Describe the Brain component of the CNS

It is the central control organ composed of:

• Grey Matter (exterior of brain)

• White Matter (interior)

What is Myelination?

Myelination is the process of forming a myelin sheath around axons to increase speed of signal transmission

• Oligodendrocytes in CNS

• Schwann cells in PNS

Describe the Spinal Cord component of the CNS

It links between the brain to the rest of the nervous system by transmitting impulses to/from brain :

• Grey matter is interior

• White matter surrounds the gray matter

Functions: Reflex Action

What is a Reflex Action

It is a rapid, involuntary response to a stimulus from the spinal cord.

What is the Peripheral Nervous System (PNS)

It transmits to/from CNS using sensory receptors, nerves.

Nerve types:

• Cranial Nerves, Spinal, Afferent, Efferent.

What are Cranial Nerves ?

Originate in hind part of brain & innervate the head and face

What are Spinal Nerves ?

Originate in spinal cord & innervate the entire body

What is the Afferent(Sensory) functional component.

Afferent neurons serve as input: sensory receptor → CNS

2 Types of sensory neurons:

1. Visceral → Not aware of (e.g., blood pressure level)

2. Somatic → Aware of (e.g., vision)

What is the Efferent (Motor) functional component.

Efferent neurons serve as output: → CNS → Effectors

• Two components:

  1. Motor System → Efferent neurons that affect skeletal muscle (voluntary movement)

  2. Autonomic Nervous System → Involuntary control of smooth muscle, cardiac muscle, glands

List the three divisions of the Autonomic Nervous System

1. Sympathetic

2. Parasympathetic

3. Enteric (digestive tract, gall bladder, and pancreas)

Describe the Sympathetic Nervous System

“Flight or Fight”

Used to jumpstart the body

SEQ the pathway of a nervous signal

1. Stimulus

2. Sensory Receptors detect the stimulus

3. Afferent Neuron carries signal to CNS

4. Central Nervous System (CNS) processes the signal

5. Efferent Neuron carries response signal

6. Motor System or Autonomic Nervous System directs the response

7. Effector (muscle or gland carries out the action)

The relative size across vertebrae brains reflects the importance of particular functions.

Sequence Brain Development

1. Embryo develops into neural tube

2. Single tube of tissue

3. Posterior becomes spinal cord

4. Anterior→ folds over→ brain

List the structures of the Brain

1. Cerebrum (Left & Right)

2. Cerebellum

3. Diencephalon (Thalamus & Hypo Thalmus)

4. Brainstem

Describe the functions of the Cerebrum

It is used for voluntary movement, learning, & “High-order thinking”:

• Divided into Left and Right Hemispheres:

  • Each hemisphere controls and perceives the opposite side of the body.

• Corpus Callosum:

  • A thick band of axons that connects the left and right halves of the brain, allowing communication between them.

Describe the functions of the Cerebellum

Located at the back of the brain used for movement, balance, position of joints.

• Takes input from the eyes (vision) and ears (inner ear - vestibular system) to maintain balance and posture.

Describe the functions of the Diencephalon

2 Components:

Thalamus: Main input center for sensory info to cerebrum & routes singlas to correct area

Hypothalamus: Regulates pituitary gland, hunger, thirst,

Describe the functions of the Brainstem

3 Parts:

1. Midbrain

   • Receives & routes sensory information

2. Pons

   • Respiratory & Sleep center

3. Medulla Oblongata

   • Basic life functions - respiration, heartbeat, BP

   • Continuous with spinal cord

How are Cnidarians Nervous System built?

They are the simplest animals with nervous systems using a:

• Nerve net: Interconnected neurons that send impulses in both directions, spread through the net. No central control organ

How are Echinoderms Nervous System built?

They use a:

• Nerve Ring: A central control strucutre

  • It signals radial nerves, which then signals muscles

How are Bilateria Nervous System built?

• Platyhelminthes to Planarians:

  • 2 longitudinal nerve cords.

  • Defined CNS.

  • Ladder-type nervous system.

• Annelids & Arthropods:

  • Use ganglia (segmentally arranged clusters of neurons).

How are Vertebrae Nervous System built?

Brain & Spinal Cord = CNS

Nerves & Ganglia = PNS

Also defined by life style (slow moving animal = simple nervous system)