NEUR 200 - Lecture 1: Neurons, Glia, and the Nervous System

What is the central nervous system (CNS) made up of?

The brain and the spinal cord

What is the peripheral nervous system (PNS) made up of?

Neurons (and neuronal tissue) outside the brain and spinal cord

*Some neurons can span both CNS and PNS

Function of the brain

Cognition, perception, emotion, behavior, motor control, regulation of bodily functions, etc

Function of spinal cord

• Carriers of sensory and motor information throughout the body

• Reflexes and pattern generators (important for things like walking)

• Function as “mini brains”

What two parts is the PNS made up of?

Somatic nervous system and autonomic nervous system

Somatic nervous system function

Sensation and control of skeletal muscles

What are the two divisions of the autonomic nervous system?

• Sympathetic nervous system and parasympathetic nervous system

• The two divisions affect your state of being

Sympathetic nervous system function

• “Fight or flight” response

• Energy expenditure and heartrate increased

• Arousal

• Mouth can dry up

• “Sympathetic” to your needs

Parasympathetic nervous system function

• Calms you down after the “fight or

• Relaxation, digestion, slowed heartrate and breathing

What are the meninges?

Series of layers that protect the brain and surround it

What fluid is between the meninges and the brain?

• Cerebrospinal fluid (CSF)

• Cushions the brain inside the skull (like bubble wrap packaging)

• Brain floats around in skull in this fluid

The menignes comprise what three layers?

The dura matter, arachnoid matter, and pia matter

What is the dura matter?

Tough outer layer of meninges

What is the arachnoid matter?

• Middle layer of meninges containing CSF and vasculature (blood vessels)

• Looks like a spiderweb

What is the pia matter?

• Soft inner layer of the meninges

• Like thin tight wrap around the brain

Explain “redundancy” in the cerebral blood supply

• Does this via the Circle of Willis (located deep in the center of the brain)

• If one part is clogged or shut down, all the other parts communicate with each other, meaning the blood supply can take a detour to get where it needs to go (like GPS rerouting)

• All arteries (the different parts) communicate with each other

What two arteries supply blood to the brain?

The carotid arteries and the vertebral arteries

Function of blood brain barrier

• Protects the brain from substances toxic to it (blood and foregin substances like pathogens or drugs)

• Allows nutrients and oxygen to get to the brain

The cells that comprise the blood brain barrier are like any other cell in that they have a cell membrane. WHAT are cell membranes made of and WHY might this be important (with respect to the BBB acting as a barrier)?

Cells are made of phospholipid bilayer, meaning that drugs that are hydrophilic will be more psychoactive

What is gray matter?

Collection of nerve cell bodies (somas)

What is white matter?

Collection of axons

Nucleus

• Ganglion in PNS

• Dense cluster of neurons (gray matter area)

Ventricles

Fluid filled cavities where metabolic byproducts accumulate and drain into venous circulation (network of blood vessels carrying them to the heart)

What are tracts in the nervous system?

• Axon bundles in the CNS

• Large groups of axons often travel together as they go from one place to the next

What are nerves?

Axon bundles in the PNS

How many cranial nerve pairs are there?

12

How many spinal nerve pairs are there?

31

What are cranial nerves?

• Emerge directly from brain

• Mainly serve head, face, and neck

What are spinal nerves?

• Emerge directly from spinal cord

• Mainly serve trunk, arms, and legs (everything below neck)

• Also relate to breathing

What is the cerebral cortex?

• Most “evolved” part of the human brain

• Functions include sensation, movement execution and planning (what will I do today?), and cognition/learning

Why is the cerebral cortex folded?

More neurons can be packed in due to an increase of surface area

Gyrus (gyri plural)

The ridges of the cerebral cortex (outer part of folds)

Sulcus (sulci plural)

Valleys of the cerebral cortex (inner part of the folds)

What is the brainstem

• Considered the oldest evolutionary part of the brain

• Continous with spinal cord

Function of brainstem

Controls automatic and vital functions such as respiration, heartrate, and digestion

What is the cerebellum?

• Critical in regulation of fine movement, coordination, timing of movements, and postural control

• Densely packed and houses half of the total CNS neurons

• Also called the hindbrain (located in the brain’s behind)

What is the cerebellar cortex?

The cortex of the cerebellum

What are Purkinje cells?

• Cells located in the cerebellar cortex

• Activity changes when we learn how to make and time movements (coordinating your movement with the time it takes to do them)

What is the corpus callosum?

• Bridge between right and left hemispheres

• Made up of white matter

What is the thalamus?

• Interacts with the cortex, relays input and output dynamics

• Central headquarters of the brain (located in center)

• Input travels here before going to other parts of the brain

What is the hypothalamus?

Controls survival functions like eating, drinking, body temperature, and fear

Medial

Towards midline

Lateral

Further from the midline

Dorsal

Toward the back, or top of head in species where the spinal cord bends

Ventral

Toward the front, or bottom in species where the spinal cord bends

Anterior

Towards the front

Posterior

Towards the back

What are glial cells?

• Support cells of the nervous system

• Transport nutrients, neurotransmitter trafficking, myelination, and responding to injury

• Less dynamic activity than neurons and do not span great distances (local)

What is myelin?

• Insulation on axons (most of them are myelinated)

• Helps axons conduct signals (make signals faster)

What are the two types of glial cells?

Macroglia and microglia

What are astrocytes?

• A type of macroglia

• Nutritive function, involved in metabolism and neurotransmission, and work with microglia to remove dead neurons after brain injury

What are oligodendrocytes?

Type of macroglia that create the myelin sheath on CNS axons

What are schwann cells?

Type of macroglia that myelinate PNS axons

What is the function of microglia?

• Janitors of the nervous system (help clean up the area)

• Mobilized after injury, infection, or disease

What does it mean for neurons to be polar?

There is a voltage difference between inside them and their outside environment

What fluid is outside the neuron

Extracellular fluid

What fluid is inside the neuron?

Intracellular fluid

What is the soma?

Cell body of the neuron that contains mitochondira, nucleus, ribosomes, etc.

What are dendrites?

The receiving ends of a neuron

What is the axon?

• The sending end of a neuron for a signal (output structure)

• Can be short (nearby signals) or long (for sending signals as far as the legs)

• Typically only one of them in a neuron

What are efferent neurons?

• Neurons that help carry information out (exit)

• Example is motor neurons

What are afferent neurons?

• Neurons that bring information in

• Example is cells in the eye that bring visual information in

True or false: Neurons with different functional roles often have different morphology/anatomy

True

What do multipolar neurons look like?

• Have many dendrites (at least 2 major branches) and one axon

• Very common in the cortex

What are unipolar/monopolar neurons?

• Neurons that have an axon branching in two directions (input zone and output zone)

• The axon acts both as dendrite and axon

• Seen in peripheral sensory neurons

What are bipolar neurons?

• Has one dendrite and one axon (two outgrowths from the soma)

• Seen in sensory systems