L06: Neurobiology Flashcards
Human Nervous System
A network of neurons that transmits signals throughout the body.
Central Nervous System
Consists of the spinal cord and brain
Spinal cord
Nerve cable that emerges from the base of the brain and extends about 2/3 of the way down the vertebral column,
Peripheral System
Nervous system outside of the CNS. Includes the somatic and autonomic systems.
Somatic Nervous System
Transmits signals to CNS from muscles and joints via nerves.
Autonomic Nervous Systems
Regulates the internal environment of the body. Stimulates glands and organs. Divided into sympathetic and parasympathetic signaling.
Sympathetic Signalling
Prepares the body for action. Chronic stress leads to increased activity of this system.
Parasympathetic Signalling
Returns the body to resting state
Endocrine System
A communication network that influences thoughts, behaviours, and actions through hormones.
The endocrine system is primarily controlled by ___
the hypothalamus
T or F The endocrine system signals slower than the nervous system
True
Glial Cell
An essential part of the nervous system allowing neurons to function (Glia means “glue” in Greek). There are microglia and there are macroglia
Microglia
Smaller glial cells, responsible for protecting the CNS. They can metabolize dead tissue and are involved in keeping the CNS healthy
Types of Macroglia
Astrocytes and Oligodendrocytes
Macroglia
Larger glial cells.
Astrocytes
Link neurons to blood vessels, forming part of the blood-brain barrier. They engulf synapses (where neurons connect), regulating neurotransmitter release during synaptic transmission
Oligodendrocytes
they surround axons in the CNS, forming the myelin sheath that insulates axons, which allows the electrical signal that travels in the axon to travel faster
Soma
A neuron’s cell body
Axon Hillock
The axon hillock is located at the end of the soma and controls the firing of the neuron.
Axon
carries nerve impulses away from the cell body
Myelin Sheath
An insulating layer that allows electrical impulses to transmit quickly and efficiently along the nerve cells
Node of Ranvier
Periodic gap in the insulating sheath (myelin) on the axon of certain neurons that serves to facilitate the rapid conduction of nerve impulses
Axon Terminal
The sites where synapses with other neurons are found, and neurotransmitters are stored there to communicate with other neurons via these synapses.
Terminal buttons
Located at the end of the neuron and are responsible for sending the signal on to other neurons
Synapse
A structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron
Dendrite
Appendages that are designed to receive communications from other cells
Vesicle
Store various neurotransmitters that are released at the synapse
Neurotransmitter
Chemical messengers in the body. Their job is to transmit signals from nerve cells to target cells.
Presynaptic cell/ terminal
the cell that releases neurotransmitters that will stimulate the postsynaptic cell. separated from the other neuron by the synaptic cleft
Post synaptic cell/ terminal
The receiving part of the synapse b/n two neurons
Information flow in the neuron
- A signal is received at the dendritic spines, at the post-synaptic terminals, where the neuron synapses with the axon of another neuron.
- This signal can produce an electric current that travels from the dendrite to the soma of the neuron.
- If the signal accumulating at the axon hillock in the soma is strong enough, the receiving neuron will “fire”, i.e., it will produce an electrical impulse at the axon hillock.
- This electrical impulse travels down the axon toward the terminal buttons (the pre-synaptic terminals).
- When the electrical impulse reaches the pre-synaptic terminal, it can produce a chemical signal: the release of neurotransmitters.
- When neurotransmitters reach the post-synaptic terminal of the receiving neuron: Go back to point 1 above.
Three types of neurons
Interneurons, sensory neurons, and motor neurons
Interneurons
Are neither sensory nor motor but connect neurons with other neurons. Located in the CNS
Sensory Neurons
Act as receptors of stimuli, or are connected to receptors
Motor Neurons
Connect the CNS to muscles, organs, & glands
t or f sensory neurons are located in the CNS
false
t or f motor neurons are located in the CNS
false
Electrical potential
how much energy is stored up in a system
what is the resting potential of a neuron?
-70 mV
Diffusion
pushes particles against their concentration gradient
Electrostatic pressure
equally electrically charged particles repel each other, and differently charged particles attract each other.
Ion channels
When proteins in the neuronal membrane that form little channels connecting the inside of the neurons with the outside and allow certain types of ions to pass
Action potential
Fired when electrical stimulation exceeds the threshold of excitement.
Action potential propagation
Generated in the body of the neuron and propagated through its axon.
Action potential steps
- Sodium channels open
- Potassium channels open
- Depolarization
- Sodium channels close
- Repolarization
- Potassium channels begin to close
Action potential in myelinated vs. unmyelated axons
myelinated- faster (speed approx. 100 m/s)
unmyelinated- slower (speed approx. 1 m/s)
effect of larger diameter on the velocity of an action potential
larger diameter = faster
Sodium- potassium pump
maintains the internal concentration of potassium ions [K+] higher than that in the surrounding medium (blood, body fluid, water) and maintains the internal concentration of sodium ions [Na+] lower than that of the surrounding medium
Synaptic Cleft
the space that separates a neuron and its target cell at a chemical synapse
Synaptic Vesicle
Small, electron-lucent vesicles that are clustered within the synapse. They store neurotransmitters and release them at the synapse.
Inhibitory neurotransmitters
They make it less likely that the post-synaptic neuron will fire
Excitatory neurotransmitters
They make it more likely that the post-synaptic neuron will fire
Presynaptic membrane
The cell membrane of an axon terminal that faces the receiving cell
Postsynaptic membrane
The membrane that receives a signal (binds neurotransmitter) from the presynaptic cell and responds via depolarisation or hyperpolarisation
Steps in signal transmission at synapse
- Transmitter is synthesized and stored in vesicles
- An action potential invades the presynaptic terminal
- Depolarization of the presynaptic terminal causes the opening of voltage-gated Ca2+ channels
- Influx of Ca2+ through channels
- Ca2+ causes vesicles to fuse with presynaptic membrane
- Transmitter is released into the synaptic cleft
- Transmitter binds to receptor molecules in postsynaptic membrane
- Opening or closing of post-synaptic channels
- Postsynaptic current causes inhibitory or exhibitory postsynaptic potential that changes the excitability of the postsynaptic cell
- Retrieval of vesicular membrane from the plasma membrane
Hemispheres
Left- critical for language
Right- critical for spatial relationships
Sulcus
a depression or groove in the cerebral cortex
Gyrus
a ridge on the cerebral cortex
Lobes
Front lobe, parietal lobe, temporal lobe, occipital lobe
Fissure
a deeper grove and is often used interchangeably with sulcus
Corpus callosum
Millions of myelinated axons that connect the two hemispheres of the brain
Contralateral hemispheric organization
Left side controls the right half of the body and vice versa
Neocortex
Part of the human brain’s cerebral cortex where higher cognitive functioning is thought to originate from
Frontal lobe
thought, planning, cognition, memory and movement
Parietal lobe
touch and spatial relations. integrating info from senses
Temporal lobe
hearing, memory. contains the hippocampus
Occipital lobe
visual processing centre
Somatosensory and motor homunculus
a topographic representation of the body parts and its correspondents along the precentral gyrus of the frontal and parietal lobes
Medulla
The lowest portion of the brain stem. Critical role in transmitting signals b/n the spinal cord and higher parts of the brain.
Pons
Connects the cerebral cortex with the medulla. Helps transfer nervous system messages b/n various parts of the brain and the spinal cord
Reticular activating system
Network of neurons located in the brain stem that project anteriorly to the hypothalamus to mediate behaviour
Brain stem
Responsible for basic survival functions such as breathing and swallowing
Cerebellum
Critical for maintaining proper motor function, memory, planning, language, and emotions. “Little brain” located at the back of the head, below the temporal and occipital lobes and above the brainstem.
Thalamus
Gateway to the cortex that received all sensory modalities (except odour). Located near the centre of the brain
Basil Ganglia
Critical for planning and movement. Includes the nucleus accumbens which is responsible for reward processing. Located deep in the brains’ hemispheres
Limbic system parts
Prefrontal cortex, hippocampus, amygdala, hypothalamus, cingulate gyrus
Prefrontal cortex
Located at the front of the frontal lobe. It is implicated in a variety of complex behaviors, including planning, and greatly contributes to personality development
Hippocampus
Essential for episodic and spatial memories
Amygdala
Processes emotions and modulates the hippocampus
Hypothalamus
Located in the centre of the brain. plays an important role in hormone production
Cingulate Gyrus
Involved in processing emotions and regulating behaviour. Located in the centre of the brain