UNIT 4 STUDY GUIDE - INTRO TO NERVOUS SYSTEM

What is a neuroglial cell?

"Helper" cells, support and nourishment

Schwann cells PERIPHERAL NERVOUS SYSTEM

- (PNS) - (Flattened wrapping cells) - Form myelin sheath for PNS Parts - Neurolemma = Cell body with cytoplasm, organelles, etc. - Myelin sheath

Depolarization

- A decrease in membrane potential Inside of the axon membrane becomes less negative - INCREASES the probability of generating an action potential

Hyper-polarization

- An increase in membrane potential - Inside of the axon becomes more negative - DECREASES the probability of generating an action potential.

Central Nervous System (CNS):

- Brain & Spinal Cord - The main control center!! - Interprets sensory input (from afferent neurons) and coordinates a response - Helps maintain homeostasis - Integrates sensory information - Coordinates conscious and unconscious activity BRAIN: - Thinking - Feeling - Remembering SPINAL CORD: - Conducts two ways signals between your brain and the rest of your body

What is a neurotransmitter and how do they work?

- Chemical messengers that allow signals to cross synapses and transmit information from a nerve cell or neuron to a target cell. They coordinate behavior by stimulating an action or inhibiting an impulse - Chemical messengers of the nervous system ... help "bridge the gap" between neurons or between neurons and their effectors

Be able to describe a resting membrane potential (RP) and understand what physiologic processes are involved in maintaining the RP (including the ions involved and where they are located).

- Concentration is much higher on the outside of the cell (Na+) - Potassium ions (K+) much greater on the inside of the cell. - The intracellular charge is slightly negative, outside the membrane it is slightly positive. Caused by selective diffusion across the membrane. - (Channel proteins) they are specific and only let a certain type of particle to diffuse through them, potassium and sodium channels. - These channels allow charged ions to move along their concentration gradient through facilitated diffusion. - Potassium channels are "leaky", meaning potassium is allowed to leave the cell. - The potassium leaving causes the slight negative charge inside the membrane - Na+ tends to diffuse into the cell, but the sodium channels aren't as "leaky" as the potassium channels. - So less sodium diffuses in then potassium diffusing out. - Maintained by the sodium-potassium pump (transmembrane carrier protein) - The pump exchanges 3 sodium out for ever two potassium in - 70 milivolts

Peripheral Nervous System (PNS)

- Cranial Nerves and spinal nerves - Communication lines between the CNS and the rest of the body Split into two divisions... Sensory (afferent) Division - Picks up sensory stimuli - Somatic (pain, touch, temperature) and visceral (pain) sensory nerve fibers - Conducts impulses from receptors to the CNS & Motor (efferent) Division - Motor nerve fibers - Conducts impulses from the CNS to effectors (muscles and glands) aka..sends directions from your brain The efferent division is split into two systems Somatic Nervous System VOULUNTARY - Somatic motor (voluntary) - Conducts impulses from the CNS to skeletal muscles - So yeah...skeletal muscle movement & Autonomic Nervous Systen (ANS) INVOULUNTARY - Visceral motor (involuntary) - Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands - Keeps your heart beating, lungs breathing, and stomach churning. The automatic nervous system is split into two more parts All things that you do not consciously control. Sympathetic Division - Mobilizes body systems during activity - excite body systems (sounds internal alarm bells) - the fight or flight response & Parasympathetic Division - Conserves energy - Promotes housekeeping functions during rest - Relaxes the body (resting & digesting)

Unipolar neurons

- Mostly in PNS - Most sensory (afferent) neurons - only one process and found in sensory receptors

Microglia (neuroglial cell) CENTRAL NERVOUS SYSTEM

- Phagocytic cells - DEFEND - Immune defense against invading microorganisms

Astrocytes (neuroglial cell) CENTRAL NERVOUS SYSTEM

- Produce neurotransmitters - Regulate K+ ion - Bind blood vessels & neurons (support) - Control the blood/brain barrier - exchange materials between neurons and capillaries - most abundant - anchor neurons to their blood supply

Ependymal cells (neuroglial cell) CENTRAL NERVOUS SYSTEM

- Produce/Circulate cerebral spinal fluid (CSF) - Look like simple cuboidal with cilia - Epithelial cells, cover the surface of the ventricles - create, secrete, and circulate spinal fluid that fills cavities and cushions organs

Oligodendrocytes (neuroglial cell) CENTRAL NERVOUS SYSTEM

- Support/ Connect - Secrete myelin for CNS neurons - wrap and insulate - form the myelin sheath

Blood-brain barrier

- barrier between blood stream and extracellular space of the brain, allowing only certain substances such as oxygen, water, and small lipid substances to easily pass from the blood into the brain. - this prevents toxins, pathogens, and other potentially dangerous substances from crossing from the circulatory system into the brain. - endothelial cells form tight junctions the restrict diffusion across the blood vessel lining. - astrocytic end-feet completely surround these blood vessels in the brain, sending signals to the endothelial cells to form the tight junctions necessary to create the blood-brain barrier. They also have functions in maintenance and regulation of the blood-brain barrier.

What is a ganglion?

A swelling, associated with nerve cell bodies. A collection of nerve cell bodies located outside the central nervous system. Located in the autonomic nervous system and sensory system. Ganglia house the cells bodies of afferent nerves and efferent nerves. - Cluster of nerve cell bodies that house millions of synapses * - A collection of nerve cell bodies located outside the central nervous system.

Define pre-synaptic membrane, synaptic cleft, and post-synaptic membrane.

A synapse is the meeting point between two neurons. Pre-synaptic membrane: The cell that's sending the signal, transmitting through a knob-like structure called the presynaptic terminal or axon terminal. Synaptic cleft: A gap between the axon of a neuron and the dendrite (or cell body) of another. Electrical activity in the neuron causes release of chemicals (neurotransmitters) into the gap Post-synaptic membrane: Accepts the neurotransmitters in the receptor region of the dendrite.

Be able to label the parts of a neuron and understand the physiology.

Axon: Conducts information (nerve impulses) away from the cell body, toward other neurons (or target cells) - the "talker" - transmit electrical impulses away from the cell body to other cells - carries impulses away from the cell body. Myelin sheath (Myelin - lipid) - Protective, insulating covering of some axons - Formed by lipid-like neuroglial cells called Schwann cells which wrap themselves around the axon many times - Gaps in the myelin sheath are called nodes of Ranvier Myelin sheath in important in - Nerve regeneration in the PNS - Protection - Increasing the SPEED of the action potential Cell body: Contains the nucleus - aka. soma, cyton, or peikaryon (these are other names) - Houses the organelles - mitochondria, golgi bodies, Nissl body (or rough ER) - Cells life support - Has stuff like nucleus, DNA, mitochondria, cytoplasms, ribosomes Dendrites: (many) - Extensions from the cell that receive information and send it towards the cell body - "the listeners" - receive impulses and carry them torwards the cell body Synapse: Neuronal junction where electrical impulses are transferred from one cell to another

What organs are found in the dorsal body cavity?

Brain & Spinal Cord - cranial cavity: space formed by the bones of the skull, contains the brain - spinal cavity: space formed by the bones of the vertebral column, contains the spinal cord.

What ion is required for neurotransmitter release into the synaptic gap?

Ca2++

Be able to describe an action potential (AP) and understand what physiologic processes are involved (including the ions involved and where they are located).

Carry information through the nervous system. Stimulation of a dendrite or cell body causes a sudden change in the permeability of the cell membrane. (DEPOLARIZATION STARTS ACTION POTENTIAL...depolarization = sodium ions rushing in) - Starts with the neuron in resting potential, all the ion channels are closed - The some environmental stimulus occurs - Triggers sodium channels to open, increasing the charge inside membrane. - This is an ALL or NONE phenomenon, (55mv) if it doesnt hit that level it's like a false alarm. And the neuron returns to it's resting state. - Then voltage gated sodium channels open, tons of them, all of the positive sodium ions rush in, making the cell massively depolarized, so much so that it goes positive - kicks off a biological chain reaction, sending the electrical signal down the axon - then repolarization kicks in - voltage gated potassium channels open up so potassium ions flow out in an attempt to rebalance the charges. - action potentials travel away from the soma toward the axon terminal. - repolarization is when potassium ions rush out again.

What is gray matter?

Cell bodies + non-myelinated fibers

What is a neuron?

Cells that transport nerve impulses (information) throughout the body - Nerve cells which respond to stimuli and transmit signals - has processes which are used to communicate / interact with other nerve cells and or epithelial and muscle cells

Understand the difference between a chemically-gated ion channel and a voltage-gated ion channel.

Chemically Gated Channels: these open in response to a specific chemical stimulus (E.g: neurotransmitter, such as acetylcholine, or a hormone); these are specifically important a synapses Voltage-gated Channels: Open and close in response to changes in membrane potential. these open in response to a change in the membrane potential; these are important in conducting action potentials along axons. Open at the end of the pre-synaptic terminal that release calcium that then release into the neurons cytoplasm. - Control the passage of ions through the cell membrane and exist along the entire length of the axon.

Be able to explain converging and diverging neuronal pathways.

Convergent pathways: Come from lots of neurons to a specific place. Ex; Rod converge on the bipolar cells in the retina Diverging neurons: One neuron sends information to many neurons. Wide area. - Temperature control - hypothalamus having a neural pathway that diverges into branches which lead to sweat glands, skin arterioles, and skeletal muscles

Define epineurium, perineurium, endoneurium.

Epineurium: outer connective tissue layer, very strong & resistant. runs around the outside of the nerves bundle everything together. Perineurium: wraps around the fascicle, holding all the contents within. Endoneurium: a layer of delicate connective tissue, encloses the myelin sheath of individual nerve fibers or axon within a nerve.

Explain the difference between and excitatory and inhibitory post-synaptic potential.

Excitatory post-synaptic potential: Graded potentials that push the neuron closer to threshold, and make an action potential more likely. They depolarize the post-synaptic neuron by making the inside of it more positive bringing it closer to it's action potential threshold. Making it more likely to send the message to the next neuron. - Increase the likelihood of the firing action potential. Stimulate the release of neurotransmitters. Inhibitory post-synaptic potential: Push the neuron further from threshold, make an action potential harder to acheive. Hyperpolarize the post-synaptic neuron by making the inside of it more negative, driving it's charge down away from the threshold. Message doesn't get moved along. - Decrease the likelihood of the firing action potential in a cell. Inhibit the related of neurotransmitters.

Where is this white and gray matter tissue found in the spine?

Gray matter is shaped like an H surrounded by white matter. Decending tracts in the spinal cord bring information from the brain, ascending tracts in the spinal cord take information to the brain.

What are the membranes of the dorsal body cavity?

Meninges

Multipolar neurons

Most in CNS - 3 or more processes sticking out from the soma (or cell body) including an axon and a bunch of dendrites

What is white matter?

Most of the myelinated axons Myelinated axons collected in bundles called tracts in the CNS and myelinated nerves in the PNS

Efferent neuron (Motor neuron)

Motor, conducts messages away from the CNS to an effector (muscle cell or gland) - multipolar neurons - transmit impulses away from the central nervous system and out to the bodies muscles=- or glands

What is a nerve? What is a tract?

Nerve: Cable-like bundle of axons in the PNS. Surrounded by three connective tissue wrappings - Endoneurium - Perineurium -Fascicles - Epinerurium A nerve is a collection of nerve fibers (axons) in the peripheral nervous system. Tract is a collection of nerve fibers (axons) in the central nervous system (CNS)

What basic tissue type is/are important in the nervous system?

Nervous Tissue - densly packed with cells - have neurons - Cells that comprise the central nervous system and peripheral nervous system. - responsible for movement, sensing, and thinking (cells are able o transmit messages between them) - sensory input and integration - the ability to receive and process information from the external environment - neurons are able to transmit electrical impulses from one site in the body to the other - controlling muscles and glands: some subtypes of neurons are able to receive signals from the brain and spinal cord which can cause muscle contraction and affect glands -homeostasis: nervous system helps maintain this equalibrium - brain is composed of nervous tissue

Where do we usually find acetylcholine, nor-epinephrine, epinephrine, dopamine, and other neurotransmitters discussed in class?

Neurotransmitters are stored in a synapse in synaptic vesicles, clustered beneath the membrane in the axon terminal located at the presynaptic nerve terminal.

Understand and describe the physiology behind the refractory period.

No more action potentials can be generated by this axon until the resting membrane potential is restored. The Na+/K+ pump re-establishes the original concentrations of ions and the neuron is ready for the next action potential (repolarization)

Bipolar neurons

Rare (retina, inner ear, olfactory) - 2 processes, an axon and a single dendrite, extending from opposite sides of the cell body

Afferent neuron (sensory neurons)

Sensory, takes messages to the CNS from a sensory receptor - pick up messages and transit impulses from sensory receptors toward the CNS - mostly unipolar

Be able to list from superficial to deep and from deep to superficial)

Superficial -> Deep Duramater: Attaches brain to skull to keep them from being rustled around. Arachnoidmater: strands of tissue called arachnoid trabeculae stretch between the arachnoid and piamater. These help to suspend the brain in place. Piamater: Closly follows the contours of the brain. Acts as an additional barrier and aids in the secretion and containment of cerebralspinal fluid.

Satellite cells PERIPHERAL NERVOUS SYSTEM

Support cells in the PNS - surround neuron cell bodies

In what ways are neurotransmitters usually removed from the synaptic cleft?

To remove the neurotransmitter it can either be destroyed by enzymes in the synaptic cleft or it can be taken back into the presynaptic axon terminal by a process called reuptake.

Where is this white and gray matter tissue found in the brain?

White matter in the middle, gray matter surrounding it. The cerebrum and cerebellum have islands of gray matter within white matter, as well as an outer cortex of gray matter. The brain stem has additional regions of gray matter (brain nuclei) buried within the white matter.