Chapter 5 Flashcards
What’s a receptor protein?
A protein that is sensitive to and capable of communicating some signal.
What types of receptors are there?
Ionotropic and Metabotropic
What is an ionotropic receptor?
A receptor protein that is an ion chanel
What determines if an ionotropic receptor will produce EPSP or IPSPs?
The properties of the pore of the ion channel
What is the effect of the activation of an ionotropic receptor
Immediate change in the permeability of the membrane to specific ions
What is a metabotropic receptor?
A receptor protein that is not an ion channel
What do metabotropic receptors typically trigger? What do they produce?
They typically trigger an intracellular signaling cascade that involves g proteins.
They can produce a variety of cellular effect
What is special about the effect of metabotropic signaling? Why?
They can be large but they are often delayed.
Because they rely on signaling cascades and diffusion
What are GPCRs (g protein coupled receptors)?
Metabotropic receptors
What do ionotropic receptors “turn toward” in order to mediate their effect?
ions
What do metabotropic receptors turn towards to mediate their effects?
metabolism
What does metabolism refer to?
Chemical reactions that occur inside of cells
What do activated metabotropic receptors trigger? What is the end result?
Intracellular signals to catalyze chemical reactions.
Almost anything, but usually a change in gene expression or the opening of intracellularly gated ion channels
How do most metabotropic receptors mediate their effects?
Activating g proteins
What does the name “g” protein symbolize?
That these proteins use GTP molecules, instead of ATP molecules, for the energy they need to perform chemical reactions
What happens when a g protein is bound to GTP? Why?
It is “on” or activated. Because in this state, it can trigger chemical reactions
When a g protein is bound to GTP and can trigger chemical reactions, is this state temporary? why or why not?
Yes, it’s temporary because G proteins have a natural tendancy to convert GTP into GDP
What happens when a G proteins converts GTP into GDP?
The g protein is “off” or inactive
How can G proteins let go of GDP?
It’s hard, they can only let go of it by finding an activated metabotropic receptor. They use the intracellular side of an activated metabotropic receptor to pry off their GDP molecule. When this happens the G protein is “off” or “inactived
What is the activation cycle of g proteins?
- Ligand binding to a metabotropic receptor
which induces… - Conformational change that facilitates the exchange of GDP for GTP on the a subunit of the G protein complex
- The g proteins then disassociate and diffuse away to activate downstream enzymes
- Once the GTP molecule is metabolized (GTP to GDP) the original G protein coupled receptor complex is restored
What is a G protein-gated ion channel?
An ion channel gated by G proteins
What are G proteins family?
A family of intracellular proteins that are involved in intracellular signaling cascades
Give a generalized illustration of a metabotropic GPCR receptor causing ion channel opening.
- Neurotransmitter binds to a metabotropic receptor
- Activated G proteins transmit the message intracellularly
- Some ion channels are gated (directly or indirectly) by activated g proteins
What can G protein signaling cascades affect?
Multiple downstream processes:
-opening g protein gated ion channels
- changes in gene transcription
- secretion of substances from the cell
… really anything the cell wants
Where can synapses from?
Between axon terminals and ….?
- Dendrites (dendritic shafts)
- dendritic spines
- Soma (cell body)
- Other axon terminal (axoaxonic synapses)
What are axoaxonic synapses?
axon terminals on other axon terminals
What do axoaxonic synapses do?
Regulate the amount of neurotransmitter that the second neuron will release when it has an action potential.
What is presynaptic inhibition in axoaxonic synapses?
Axoaxonic synapses can hyperpolarize the axon terminal of the downstream neuron, so that its voltage gated calcium channels will not open at all or for very long when an action potential arrives. The effect: reduce neurotransmitter release when it has an action potential
What is presynaptic facilitation in axoaxonic synapses?
Axoaxonic synapses can depolarize the axon terminal of the downstream neuron, so that its voltage gated calcium channels are more likely to open when an action potential arrives. Effect: increase neurotransmitter release when it has an action potential
What is an autoreceptor?
A receptor located on the presynaptic membrane that gets activated when the cell releases its own neurotransmitter
What are autoreceptors gated by?
The neurotransmitter that the cell releases
Are autoreceptors generally metabotropic/ionotropic? Inhibitory or excitatory?
Metabotropic and inhibitory
What is the main source of presynaptic inhibition?
Autoreceptors
What is the postsynaptic receptor?
The receptor located on the receiving neuron, the one that is not releasing the neurotransmitter
What is the CNS (central nervous system?
Everything in the brain and spinal cord
What is the PNS (peripheral nervous system)?
Any part of the nervous systejm outside the brain and spinal cord, including the nerves attached to the brain and spinal cord.
What is the difference between the production of myelin in the CNS and PNS
In the CNS: myelin is created by oligodendrocytes
In the PNS: myelin is created by schwann cells
What is the blood brain barrier?
The semipermeable barrier between the blood and the brain
Where does extracellular fluid come from outside the brain and spinal cord?
blood
How does plasma leak out of the blood vessels in the body? What is this called?
Blood vessels have little holes in them, which allows blood plasma to leak out.
Lymph.
What does lymph do?
Flows around cells, providing nutrients and collecting waste.
Where is lymph collected? Where is it brought to? What do these structures do?
It is collected into lymph vessels.
It is brought to lymph nodes/lymph organs.
These structures detect and destroy any invading organisms of foreign particles and then they return the lymph back to the blood to start the process again.
Does the CNS particpate in the lymphatic system? Why? What’s this property called?
No.
Because the blood capillaries that pass through the brain and spinal cord do not have gaps in them.
The blood brain barrier.
What does the CNS do instead of lymph?
It makes its own extracellular solution by picking out exactly what it needs from the blood. The solution it makes is called cerebrospinal fluid (CSF)
What are meninges?
Tough, protective connective tissues that surround the brain.
What is dura mater?
A meninge, the outer layer which is the thick, tough and unstretchable tissue.
What is the arachnoid membrane?
A meninge, the middle layer which is soft and spongy and has a web like appearance
What is pia mater?
A meninge, the third layer (which sits closest to the brain), this layer and the space above it has blood vessels in it
Where is the subarachnoid space? What is it filled with?
It is between the arachnoid membrane and pia mater.
It is filled with cerebrospinal fluid (CSF)
What are ventricles?
Four interconnected hollow spaces within the brain.
What is produced in the ventricles? How?
Cerebrospinal fluid.
From tissue called Choroid plexus.
Lateral ventricles:
size:
where do they sit:
Large.
underneath the cerebrum
Where does the third ventricle lie?
Between the two thalamic nulcei
Where does the fourth ventricle sit?
between the pons and cerebellum
Cerebral aqueduct:
size:
structure:
what does it connect:
long
tube like structure
it connect the third and fourth ventricle
What does CSF do before its absorbed into the blood supply?
Exits the ventricles and flows around the brain and spinal cord - in the subarachnoid space.
How often is CSF made? What is the half life?
CSF is made continuously.
It is half replaced every three hours
What is a neuron entirely located in the CNS technically called?
What is the word interneuron used to describe?
What is the term projection neuron used to describe?
Interneuron..
Only used for CNS neuons whose axons stay local : it only makes synapses on nearby neurons
Used when the axon of a cell goes outside the area where its soma is located
What system are the axons of motor neurons a part of?
the PNS
What are axons of motor neurons? which means?
What do motor neurons control?
Where is the soma of motor neurons located?
Efferent fibers : fibers that bring info away from (the CNS), the outputs.
Motor neurons control muscle contaction and gland secretion.
The soma of motor neurons is located within the spinal cord (the CNS)
What system are the sensory neurons a part of?
the PNS
What are axons of sensory neurons?
What does that mean?
What do sesnory neurons do?
Where do they send this info?
Afferent fibers: fibers that bring info towards the CNS, the inputs.
Sensory neurons detect changes in the external and internal environment.
They send this information to the CNS
How do the brain and spinal cord communicate with the rest of the body?
What are these nerves a part of?
What do they do?
Via nerves: cranial and spinal
They are a part of the PNS
They convey messages from the CNS to body’s muscles and glands
How many pairs of spinal nerves attach to the spinal cord?
How many per each vertebrae?
31 pairs.
About 1.
How many pairs of cranial nerves attach to the ventral surface if the brain?
12 pairs
Do all the cranial nerves attach to the ventral surface of the brain? Exceptions?
No, the 10th serve sensory and motor functions of head and neck region doesn’t, all the other cranial nerves do.
What is the 10th cranial nerve called? Why? What does it regulate?
It is called the vagus (wandering) nerve because its branches wander throughout the thorcic and abdominal cavities.
It regulates functions of the heart, lungs, upper digestive track and other organs in the area
What is the spinal cord?
A long cortical structure that is approximately as thick as an adult’s little finger.
What is the principal function of the spinal cord?
To distribute motor fibers to the effector organs of the body (glands and muscles) and to collect somatosensory information to be passed on to the brain
Does the spinal cord have a certain degree of autonomy?
Yes, various reflexive control circuits are located there
Describe the somatic nervous system
Interacts with external environment
Afferent nerves: Carry sensory signal from eyes, ears, skin, etc to CNS
Efferent nerves: carry motor signals from CNS to skeletal muscles
Describe the autonomic nervous system
Regulates body’s internal environment
Afferent nerves: Carry sensory signals from internal oragns to CNS
Efferent nerves: carry motor signals from CNS to internal organs
What are the two components of the PNS?
Somatic and autonomic nervous system
What is the somatic nervous system?
Part of the peripheral nervous system that controls skeletal muscle movements and processes sensory information that related to the outside world. In general the somatic system interacts with the external environment.
What is the autonomic nervous system?
Part of the peripheral nervous system that is concerned with sensation and regulation of smooth muscle, cardiac muscle and glands. In general, interacts with the body’s internal environment
What are the 2 components of the autonomic nervous system : efferent branch?
the sympathetic and parasympathetic division
What does the sympathetic division of the autonomic nervous systems efferent branch do? What does it do once stimulated?
Part of efferent autonomic nervous system that primes the body for action, in life threatening situation.
Once stimulated, it shunts blood away from organs that are necessary for immediate survival and increases blood flow to organs involved in intense physical activity
What does the parasympathetic division of the efferent autonomic nervous system do? What is it associated with? What are its functions?
Supports activities that occur when the body is in a relaxed state and all is well.
Generally involved with body’s energy stores. - Feed and breed, rest and digest
Functions include sexual arousal, defecation, urination and salvation
What do these anatomical directions mean?
Anterior
Posterior
Superior
Inferior
Rostral
Caudal
Dorsal
Ventral
Lateral
Medial
Anterior: In front
Posterior: behind
Superior: above
Inferior:below
Rostral: towards the beak
Caudal: towards the tail
Dorsal: towards the back
Ventral: towards the stomach
Lateral : away from midline
Medial: toward midline
What do we do when we’re dealing with anatomical directions in regards to the human spinal cord?
Rotate
What do these terms mean?
transverse plane:
medial:
lateral:
Sagital plane:
Horizontal plane:
transverse plane: frontal/cross/coronal section
medial: toward midline
lateral: away from midline
Sagital plane: a mid sagital cut between the eyes
Horizontal plane: top of brain cut
What do these terms mean?
contralateral:
ipsilateral:
superficial:
deep:
proximal:
distal:
brain nuclei:
contralateral: structures on other side of body
ipsilateral:structures on same side of body
superficial: located close to the surface, close to exterior of animal
deep: located far away from surface, deep in the interior of the animal
proximal: nearby
distal: far away
brain nuclei: in the brain, collection of neurons that are clustered together that all work together to serve some function
