kin 131 Chapter 7 (midterm 2) Flashcards
What are the 3 functions of the nervous system and details about them?
- Sensing
- gather and receive information from the world around us
- Receive infromation from external factors (factors around us) and internal factors (what’s happening inside of us) - Understanding (integration)
- Information received is gathered and processed - Action
- Responding to information received with an action (eg. information tells the body that its too cold leads to putting on a hoodie)
Explain the organization of the nervous system
- Central nervous system (CNS)
- Composed of the brain and spinal cord. The CNS processes the sensory information sent from the PNS to produce a appropriate response
- Peripheral nervous system (PNS)
- Composed of all nervous tissue that is not the spinal cord and brain. The PNS connects the CNS to the limbs and organs allowing for communication though the body
What two types of cells make up the nervous system? Explain what they do
- Neurons:
- Functional unit of the nervous system
- specialized cells that transfer information
- Excitable: Can conduct a electrical signal - Neuroglial cells:
- Multiple types
- support the neuron’s in many ways
- Not excitable
Explain the anatomy of a neuron
- Soma: Cell body
- Dendrites: Branch like structures that receive signals from the body and transport them into the neuron
- Axon: long structure that relays the signal out of the neuron. Starts as a single structure but branches off at the end
- Axon hillock: Region where the axon connects to the soma. Where the action potential is triggered
Axon terminal: End of each branch of the axon and is where synapse between neurons, muscle, glands occurs
Myelin sheath: fatty layer that surrounds segments of the axon, formed by glial cells (oligodendrocytes in the CNS and Schwann cells in the PNS). It insulates the axon, allowing for faster transmission of electrical impulses
Nodes of ranvier: Small gaps between the myelin sheath along the axon. Allows for depolarization and the re-strengthening of the action potential
explain the parts of Neuron development. What is this process called?
Neurogenisis: Development of the neuron
Neuroprogenetor cells: Stem cells that differentiate into neuroblasts
neuroblasts: Immature cells that forms neurons
Growth cone: Axon end of the neuron that guides the growth of the axon towards its target. Can be another neuron or a muscle
Structural classification of neurons
Unipolar:
-Structure: Has a single extension that extends from the cell body, which then branches into two parts: one that acts as a dendrite and another that acts as an axon.
-Function: Primarily found in sensory neurons, particularly in the peripheral nervous system
Bipolar:
- Structure: Has two distinct extensions: one dendrite and one axon extending from opposite ends of the cell body.
Multipolar:
- Structure: Have one axon and multiple dendrites extending from the cell body.
-Function: The most common type of neuron in the central nervous system; they are involved in various functions, including motor control and integration of information.
Functional classifications of neurons
Sensory/afferent
- Function: Transmit sensory information from sensory receptors (e.g., in the skin, eyes, ears) to the central nervous system (CNS)
Integrative/interneurons:
- Function: Takes the information from the sensory neurons and process it to make a decision. Almost completely all in the CNS
Motor/efferent
-Function: Carry signals from the CNS to muscles and glands to make a responses (e.g., movement or secretion)
Explain the difference between a nerve and a neuron
Neuron: A neuron is a single type of cell that is the basic functional unit of the nervous system
nerve: A nerve is a bundle of many axons (from multiple neurons) enclosed in connective tissueplus bloodvessels
Structure of a nerve
Nerve > Fascicles (groups of axons) > Individual axons
- Epineurium: Surrounds the entire nerve
- Perineurium: Surrounds the fascicles
- Endoneurium: Surrounds the individual axons
Neurolema: Plasma membrane of a axon
What are the neuroglia cells and their primary functions? Which nervous system are they found in?
- Astrocytes (CNS):
- Structural support
- Forms the blood brain barrier (Controls what can enter the brain)
- Microglia cells (CNS)
- Acts as the immune defence system of the brain, removing debris and dead cells
- Type of phagocyte cell
- Ependymal cells (CNS):
- Line the cavities in the brain and the spinal cord and produce cerebrospinal fluid - Oligodendrocytes (CNS):
- Produces myosin sheaths for neurons in the CNS
- One oligodendrocyte provides multiple wrappings for axons in the CNS - Schwann cells (PNS):
-Produces myelin sheaths for neurons in the PNS
- One Schwann cell = 1 wrapping - Satellite cells (PNS):
- Surrounds the cell bodies of neurons
- Regulates interaction between cell body and extracellular enviroment
Grey vs white matter and where their found in the CNS
Grey matter: Cell bodies of neurons
White matter: myelinated neurons
In the brain the white matter is found in the middle and the grey matter is found on the perimeter. In the spinal cord grey matter is found in the centre while white matter is found on the perimeter
Explain what the disease Multiple sclerosis is and how it affects humans?
-Immune system attacks the myosin sheath
- This causes the myosin sheath to not be able to transmit the signal between nodes of ranvier causing possible loss of movement in a muscle
explain Axon Injury and repair in the PNS
- Axon is broken and split fully
- Schwann cells form a cord attaching the two broken pieces of the axon together. Macrophages clean up the debris from the break
- Axon starts to regrow (1mm/day) being directed to the other side by the Schwann cell cord
- After the reconnection of the axon the Schwann cells can regrow the myosin sheath
Explain axon injury and repair in the CNS
- Axons unable to spontaneously regrow
- Since the CNS doesn’t have Schwann cells, the axons don’t get the same guidance for regrowth as they would in the PNS
- Another factor that limits repair is that if astrocytes are damages they can form scar tissue and block axonal regrowth
-Result: loss in sensation and paralysis
Explain the parts of the cell membrane
- Phospholipid bi-layer
- Has proteins embedded in it for transport, structure…
- Integral proteins: Pass all the way through the membrane
- Peripheral membrane: sits on the surface of the membrane
- extracellular fluid on the outside intracellular fluid on the inside
- main function is to control what enters and leaves the cell
What are the two types of transport across the cell membrane?
Active transport:
- ATP is used to power a protein to move something against their concentration gradient
Passive transport:
- No ATP is used
- Move with their concentration gradient
2 types of passive transport:
1. Diffusion: Can pass directly though the cell membrane
- facilitated diffusion: Diffuse through a facilitative protein
Explain the process and purpose of the Sodium/potassium pump
Purpose:
- used to maintain the correct membrane potential in the neruron.
Process:
1. Na+ enters the pump, Pi from ATP binds to the pump causing it to pump the Na+ out of the cell
- K+ enters the pump from the outside of the cell. Pi leaves, this causes the pump to change shape pumping the K+ into the cell
What’s the ratio of Na+ to K+ pumped in/out in the sodium potassium pump. What does this do?
3 Na+ pumped out for every 2 K+ pumped in. This establishes a more negative potential inside than outside
What is a cell membrane potential and what is the resting membrane potential or neurons
- A cell membrane potential is the difference between the charge outside the membrane and inside
- The resting membrane potential of a neuron is -70Mv
What’s the difference between the endometrium and the neurolemma? ASK
Endometrium: conective tissue layer of each individual axonn
Endomegtrium: Plasma membrane of the axon
What are the 4 changes in membrane potential; and what are they?
Repolarization: Potential becomes more negative towards resting membrane potential
Depolarization: Potential becomes more positive
Hyperpolerization: Membrane potential becomes more negative then the resting potential
Overshoot: Membrane potential becomes positive
What’s the definition of a action potential?
Rapid depolarization then repolerization of the membrane potential
What are the 3 phases of a action potential?
Rising: Membrane potential becomes less negative
Falling: Membrane potential becomes more negative until resting potential
After hyperpolerization: Membrane potential dips down below the resting potential then returns
What does it mean that an action potential is all or nothing? What does it take to activate a action potential?
All or nothing means that it either happens or it doesn’t.
To make this happen the critical threshold of -55mV must be reached
Explain the process of a action potential
See sheet in binder
What is the refractory period, And why does it happen?
The time after an action potential when it’s impossible to activate another action potential. This happenes because the sodium channels are not fully reset to its original state where the activation gate is closed and the inactivation gate is closed. This means that another action potential connote be activated
What is the relative refractory period?
Occurs after the refractive period, and is the time when another action potential can be initiated, but it will take a high level of stimulus for it to happen. This is because the membrane potential is still below the resting membrane potential recovering from the last action potential.
Do action potentials lose strength over time?
No
What are the two factors that affect the speed of an action potential?
Myelin: Signal is sent through the section of myelinated axon quickly and is re-supplies at the nodes of ranvier where a action potential is created.
Axon diameter: How wide is the axon? larger diameter = faster transmission of signal
Why does mylenation save energy?
Na+/K+ pumps aren’t being used to recreate the resting membrane potential because no action potential is created when mylenated
What is a graded potential?
Small local change in membrane potential
Where do graded potentials occur?
- Dendrites of interneurons
- Dendrites of motor neurons
- Motor end plates
What is the strength of a graded potential?
Depends on the strength of the stimulus up to -55mv because then it would become a action potential
does graded potentials dissipate over time? Why?
Yes, because theirs no myelin at the dendrites
What is synaptic summation and what are the two types?
Adding multiple graded potentials together to make a larger one
- Spacial summation: How many neurons are sending out graded potentials separated by space (amount of neurons sending signals). Numerous neurons send signals that sum into one
- Temporal summation: How frequent are the graded potentials coming out of each individual neurons. Higher frequency signals sum into one
How is myelin formed?
Shwann cells attach and encase an axon. Myelin grows around the axon which is covered by the Schwann cell
In which fiber type is pain first felt in? Why?
A fibers: Diameter: 5-20um
B fibers: Diameter: 2-3um
C fibers: Diameter: 0.5-1.5um
A fibres, because they have the largest diameter meaning faster action potentials
What 2 factors affect the strength of a graded potential?
-Amount of ion channels that open
-How long the ion Chanels are open for
What are the two types of graded potentials? Do they make it easier or harder to reach the critical threshold?
Excitatory: Depolarize making it easier to reach -55mV
Inhibitory: hyperpolerization making it harder to reach -55mV
What can a neuron synapse with?
- Another neuron
- Muscles
- glands
What are the two types of neuron-neuron synapses?
Chemical: Uses neurotransmitters
Electrical: Signal passes directly through from the presynaptic neuron to the post synaptic neuron
3 parts of neuron- neuron synapsis
- Pre synaptic neuron
- Synaptic cleft
- Post synaptic cleft
What are the two types of neurons coming together?
Convergence: Multiple neurons synapse with a single neuron
Divergence: One neuron synapses with multiple receiving neurons
What are the two types of receptors in postsynaptic activation and explain them?
- Ionotropic receptors:
- Linked directly to a ion channel
- Activated by a neurotransmitter attaching to it
- Fast response but short lasting - Metabotroic receptors:
- receptors linked to a separate protein called G proteins that conduct the signal either opening or closing a ion channel nearby
- indirectly linked to the ion channel
- Slower response but longer lasting
When neurotransmitters are left in the synaptic cleft what are the 4 ways they can be removed?
- Conversion: Conversion on the neurotransmitters to an inactive form via an enzyme. eg. Acetylcholinesterase
- Diffusion: Neurotransmitters diffuse out of the synaptic cleft
- Glial degeneration: Transport to a nearby neuroglia cell where their disposed of
- neurotransmiter re-uptake: Active transport is used to move the neurotransmitters back up into the pre-synaptic membrane
What graded potential can help decrease pain?
Inhibitory post synaptic potential (IPSP) because it makes it harder to create a action potential to signal pain
What are some effects drugs or diseases have on the synaptic process?
- Prevent neurotransmitter release
- prevent neurotransmitter re-uptake
- Increase amount of neurotransmitters released into synaptic cleft
What are the 3 types of neurotransmitters?
ASK
- Acetylcholine
- Released by cholinergic neurons - Catecholamines
-eg. epinephrin and norepinephrine, dopamine - Serotonin
- Excitatory pathways
- inhibitory pathways
What are the types of nerves in the CNS vs the PNS? voluntary or not?
CNS:
- Brain
- Spinal cord
PNS:
- Somatic: Control of skeletal muscle (Voluntary)
- Autonomic: Control of organs/hormones (Involuntary)
- Enteric: Control of digestion system
What regulates the membrane potential? is it passive or active?
Na+/K+ pumps: Active transport
Ion leak channel: Passive transport
Explain more about graded potential and excitatory vs inhibitory signals. What kind of questions would be asked about it?
