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neurophysiology Flashcards

neurotransmitters

1
Q

how many types of NTs can a single neuron type, release?
how do neurons respond to different NTs?

A

only one !
any given neuron can respond to several NTs

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2
Q

define the following NTs
1 Acetylcholine
2 glutamate
3 GABA
4 Norepinephrine
5 Dopamine
6 Serotonin

A

1 found in the neurommuscular synapses (autonomic NS )

2 Main excitatory NT in brain

3 Main inhibitory NT in brain

4 Autonomic NS ,learning, emotion behavioural pathways

5 learning, emotion, behavioural pathways

6 learning, emotion, behavioural pathways

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3
Q

NTs are classified by their functions.
Explain the difference between excitatory and inhibitory NTs and give examples for each type.

A
  • Excitatory NTs cause DEPOLARIZATION of post-synaptic neurons
    (eg. Glutamate)
  • Inhibitory NTs cause HYPERPOLARIZATION of post-synaptic neurons
    (eg. GABA and Glycine)
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4
Q

true / false :
Some NTs can have both inhibitory & excitatory effects

A

True

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5
Q

what determines whether a NT is inhibitory or excitatory ?

A

Determined by the receptor type of the post-synaptic neuron

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6
Q

Explain how acetylcholine can be both inhibitory and excitatory

A

acetylcholine is excitatory at neuromuscular junctions with skeletal muscle because of its NICOTINIC receptor
it is inhibitory in cardiac muscle bc of its MUSCARINIC receptor

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7
Q

Name and define the 2 types of NT receptor mechanisms

A

Direct : NTs that opens ion channels and promotes rapid responses iow “fast synapses”
- ACh and amino acids
Indirect : NTs that act through second messengers and promotes long lasting affects iow “slow synapses”
-biogenic amines, peptides & dissolved gases

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8
Q

Discuss the effects of NTs i.t.o. their receptors and how it changes the membrane potential

A

NT receptors mediate changes to the membrane potential according the the amount of NT released and the amount of time the NT is bound to receptors.
NTs will affect the membrane potential as long as they are bound thus they must be deactivated

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9
Q

How can graded potential be stopped?

A

Graded potentials will continue as long as NTs are bound to its receptor. In order to stop a graded potential , the NT must be INACTIVATED / REMOVED .

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10
Q

Discuss the 3 ways NT effects are deactivated

A

1 ACTIVE TRANSPORT
- NT will be actively pump back into the pre-synaptic cell (axon terminal ) or nearby neuroglia where they can be reused or transported into glial cells

2 ENZYMES
- Enzymes are present in the synaptic cleft that will breakdown the NT to quickly stop the signal (thus inactivating the NT)
- eg) acetylcholinterase

3 DIFFUSION
- NTs can diffuse out of the synaptic cleft to REDUCE its signal

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11
Q

Define Acetylcholinesterase & give its chemical reaction

A

An enzyme found in the synaptic cleft that degrades acetylcholine
NOTE: It assures that no excess of acetylcholine remains in the synaptic cleft to cause the continuous activation of receptors.

                   (AchE) Acetylcholine -----> Acetate + Choline
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12
Q

What are the products of acetylcholine after its broken down by Acetylcholinesterase and what happens to them ?

A

The products are acetate and choline.
Both products are reabsorbed and recycled so that they can be used again in transmitting another chemical messege. BUT
Choline is actively transported back into pre-synaptic terminal and used to reform ACETYLCHOLINE with the help of the enzyme ChAT ( Choline acetyl transferase )

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13
Q

what is Acetylcholine made up of ?

A

Choline and Acetyl CoA

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14
Q

what is the chemical reaction for the formation of Acetylcholine ?

A

ChAT
Acetyl CoA + Choline ——–> Acetylcholine

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15
Q

True / False : drugs do not alter synaptic activity

A

FALSE
Many drugs alter synaptic activity

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16
Q

What are the possible effects of drugs on synaptic activity ?
Give 2 examples

A

A-M-I-R
A- Altering synthesis , storage or release of NTs
M- Modifying NT interaction with its receptor
I- Influencing NT reuptake /destruction
R- Replacing deficient NT with a substitute NT

(examples)
=> SSRI’s
=> Tetanus Toxin

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17
Q

What is a tetanus toxin?

A

Drug
They prevent the release of GABA from inhibitory neurons at neuromuscular synapses.
- causes uncontrolled muscle spasms (too much excitation) and lock jaw

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18
Q

What are SSRI’s ?

A

Drugs
Selective Serotonin Reuptake Inhibitors
- they prevent the reuptake of serotonin thus increasing the length of time serotonin is at the synapses
- used to treat depression

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19
Q

How do neurons communicate ?

A

ELECTRICALLY through electrical gradients & CHEMICALLY through NTs

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20
Q

Define electrical Communication

A

The movement of ions in and out of cell membranes
- can be small, local or travel long distances down the branches of the cell
=> EPSPs, IPSPs & Action potencial

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21
Q

Define Chemical communication

A

The release of NTs (ligand) to nearby NT receptors (receptor) at synapses.
- effect on post-synaptic cell will depend on the NT and the receptor/ion channel interaction

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22
Q

How are the Nervous system pathways organized ?

A

Organized into complex pathways of multicellular connections. (groups of multiple cells interact as neural units)

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23
Q

Define the two different Nervous System pathways

A

Convergent Pathways: A single cell is influenced by thousands of the other cells , this is input converging on 1 cell and is a convergent pathway

Divergent Pathways : A single cell can also branch to thousands of other cells , this is input expanding from one cell to many and is a Divergent pathway

24
Q

How is the information conveyed within a neural circuit found ?

A

Found within the pattern of electrical stimulation
Graded Potentials: subthreshold electrical EPSPs & IPSPs
- INCREASE amplitude and fequency of EPSPs & IPSPs signals that more activation has occured

Action Potentials: All or None electrical propagation
- CANNOT change shape or amplitude of the AP
- INCREASED frequency or change in pattern of AP’s is used as the “coding” signal that activation has changed

25
Q

What are the two branches of the Efferent Nervous System

A

Autonomic & Somatic Nervous System

26
Q

Describe the Afferent Division of the PNS

A

Afferent division : Sensory Info IN
- receptor
- receptor potential
- sensory neuron
- AP in sensory neuron
INTEGRATION : CNS neuron (s)
- spinal or cranial reflexes
- spinal cord and brain complex sensory pathways
=> APs in CNS neurons

27
Q

Describe the Efferent Division of the PNS

A

Efferent Division: Motor respones OUT
INTEGRATION: CNS neurons
- spinal or cranial reflexes
- spinal cord and brain complex sensory pathways
- motor neuron

[ BRANCHES ]
Somatic NS = motor neurons to skeletal muscles

Autonomic NS = pre & post-ganglionic neurons to organs and glands

28
Q

What does the Somatic Nervous System control ?

A

Controls the skeletal muscles
=> VOLUNTARY , planned muscle movements and skeletal muscle reflexes
- posture
- Balance
- Body movement

29
Q

What STRUCTURES are involved in the Central Nervous System ?

A

Motor cortex
Basal ganglia
Cerebellum
Brainstem
Spinal cord

30
Q

What does the Efferent Autonomic nerve pathways consist of ?

A

a two-neuron chain between the CNS and the effector organ

31
Q

Describe the motor unit

A

Motor neuron originates at the spinal cord.
- long axon exits VENTRAL horn of spinal cord
- EXCITATORY synapses to skeletal muscle fibers
=> Neuromuscular Junction

NT present : Acetylcholine
–NT receptor: Nicotinic Acetylcholine Receptor

32
Q

Describe the events at a Neuromuscular Junction

A

1 An ACTION POTENTIAL in a motor neuron is propagated to the terminal button

2 This local AP triggers the opening of voltage gated Ca2+ channels and the subsequent entry of Ca2+ into the terminal button

3 Ca2+ triggers the release of Acetylcholine (ACh) by EXOCYTOSIS from a portion of the vesicles

4 ACh diffuses across the space separating the nerve and muscle cells & binds with receptor-channels specific for it on the motor end plate of the muscle cell membrane

5 This binding brings about the opening of these non-specific cation channels , leading to a relatively large movement of Na+ into the muscle cell compared to a smaller movement of K+ outward

6 The result is an END-PLATE POTENTIAL.
Local current flow occurs between the depolarized end plate and the adjacent membrane.

7 This local currents flow open voltage gated Na+ channels IN THE ADJACENT MEMBRANE

8 The resultant Na+ entry REDUCES THE POTENTIAL TO THRESHOLD , INITIATING AN ACTION POTENTIAL, which is propagated throughout the muscle fiber.

9 ACh is subsequently destroyed by ACETYLCHOLINESTERASE, an enzyme located on the motor end-plate membrane , terminating the muscle cell’s response

33
Q

what is the role of the Corticospinal pathway ?

A

It is the major somatic efferent pathway

34
Q

Describe the structure of the Corticospinal Pathway

A

PRIMARY MOTOR CORTEX:
- Upper motor neuron
-Cell body in the cerebrum
-Axon descends

SPINAL CORD:
-Lower motor neuron
-Cell body in the Ventral horn
-Axon exits through the Ventral Root of spinal cord

SKELETAL MUSCLE:
-Final synaps=Neuromuscular junction
-Followed by release of Acetylcholine
=> MUSCLE CONTRACTION

35
Q

Describe the role of the Autonomic Nervous System

A

ANS controls smooth muscle of the organs and cardiac muscle of the heart
- UNCONSCIOUS , organ-level reflexes

36
Q

What STRUCTURES are involved in the Autonomic Nervous System?

A

Hypothalamus
Brain stem
Spinal cord
Autonomic Ganglia

37
Q

Describe how the structures of the ANS are involved in Autonomic pathways ?

A

HYPOTHAMALUS:
-Upper , homeostatic neurons

BRAIN STEM OR SPINAL CORD:
- Cell body of pre-ganglionic neurons in brainstem OR Cell body of pre-ganglionic neurons in lateral gray horn of spinal cord
-Axons exit the ventral root
-SYNAPSE in autonomic ganglia
-NT INVOLVED: Acetylcholine

AUTONOMIC GANGLIA:
- Cell bodies of final neurons
-Final synaps= Diffuse vasicosities
-Diffuse varicosity-type synapses to whole organs
-NTs INVOLVED: Acetylcholine or Norepinephrine

EXAMPLE : Smooth muscle varicosities

38
Q

Compare the Autonomic NS vs Somatic NS

A

CNS CONTROL:
SNS= primary motor neuron
ANS= hypothamalus

LOWER MOTOR NEURON:
SNS= ventral horn to ventral root
ANS= lateral horn to lateral root (or brainstem)

PNS:
SNS= directly to skeletal muscle
ANS= first autonomic ganglia then to organs

PERIPHERAL NTs:
SNS= Acetylcholine
ANS=Acetylcholine or Norepinephrine

FINAL SYNAPS:
SNS= neuromuscular junction
ANS= diffuse varicosities

39
Q

Define the Autonomic Nervous System and its functions

A

The ANS is part of the efferent nervous system which controls responses of organs and glands

FUNCTIONS:
- involuntary regulations of homeostasis
- controls responses in the smooth muscle, cardiac muscle , endocrine glands and adipose tissue

40
Q

Describe the GENERAL ANATOMY of the ANS

A

1 Receives input from CNS regions
2 sends EFFERENT signals via 2 neurons to organs
- pre-ganglionic neuron originates in CNS
- ganglion containing cell bodies
- post-ganglionic neuron synapses diffusely with organ

41
Q

WHAT are the two branches of the Autonomic Nervous System

A

The two OPPOSING branches are :
1 SYMPATHETIC NS ( SNS )
2 PARASYMPATHETIC NS (PSNS)

42
Q

HOW do the parasympathetic and sympathetic NSs oppose each other?

A

Each branch is anatomically and functionally different
Differ in :
-length of pre and post- ganglionic axons
-location of ganglia
-NTs for post-ganglionic neurons
-receptors (adds to difference in functional effects within target organs)

43
Q

WHAT are the anatomical differences between the SNS and PSNS

A

SYMPATHETIC NERVOUS SYSTEM:
- Short axon pre-ganglionic neurons from lateral horn of thoracic and lumbar spinal cord
- Ganglion near spinal cord
^ Sympathetic Chain Ganglia
^ Collateral Ganglia
- Long axon post-ganglionic neurons to effector

PARASYMPATHETIC NERVOUS SYSTEM:
- Long axon preganglionic neurons from cranial nerves (CN III, VIII, IX, X) and Sacral spinal cord
-“terminal” ganglion, terminate IN or near the effector organ
- Short axon post-ganglionic neurons to effector organ

44
Q

WHAT are the CHEMICAL SIGNALLING differences between the SNS and PSNS ?

A

SNS:
- Pre-ganglionic NT: Acetylcholine
-Post-ganglionic NT: Norepinephrine (“Noradrenaline”)

PSNS:
- Pre-ganglionic NT: Acetylcholine
-Post-ganglionic NT: Acetylcholine

45
Q

What are the effects of the Autonomic NS ?

A

Autonomic activity affects entire organs (vs Just a few muscle fibers in the somatic nervous system) due to post-ganglionic anatomy
- DIFFUSE SYNAPSES from ANS are spread through target organs
- DIFFUSE RELEASE of NT is spread across entire organ
- GAP JUNCTIONS: Target organ’s smooth muscle & cardiac muscle are connected by gap junctions

=> each organ is independently controlled

46
Q

Discuss the REGULATORY FUNCTIONS of the ANS

A

Cardiovascular Activities:
- Cardiac ouput
- Heart rate
- blood pressure & distribution

Body Fluid Activities:
-pH
-osmolarity
-thirst
-water content

Pulmonary Activities:
- Breathing rate
- Bronchiole diameter
- O2 and CO2 content

Gastrointestinal Activities:
- Motility along digestive tract
-Mechanical and chemical digestion

Viseral Activities:
- Micturation (urination)
-Defecation
-Sexual reflexes

Stress:
- stimulates various hormones to cope with situations

47
Q

Sympathetic functions & when is it dominant ?

A

aka “flight or fight”
Dominant when body is preparing for physical activity, stress, or in threatened situations
(what dies body need to reponds to a physical threat)

> INCREASED BLOOD FLOW TO MUSCLES
- Increased heart rate
- Increased force of heart contaction
- Increased blood pressure

> OPEN AIRWAYS
- Increased oxygen

> INCREASED DISTANCE VISION
-dilate pupils

> INCREASED METABOLIC PREPARATION
- Increased RELEASE of bloodsugar and fat
- Increased sweat to anticipate excess heat production

48
Q

What structures does the sympathetic NS target to be able to serve these functions ?

A

SWEAT GLANDS
- Increased secretion

ARRECTOR PILI MUSCLE
-goosebumps

CARDIOVASCULAR SYSTEM
- Increased blood flow to brain, heart, lungs, muscles, skin
- Decreased blood flow to urinary & digestive system
- Increased heart rate, heart contraction, bloodpressure

RESPIRATORY SYSTEM
- Increased airflow

DIGESTIVE SYSTEM
-Decreased activity and secretions
- breakdown nutrient stores

SKELETAL MUSCLE
- Increased contraction force
- Increased Acetylcholine release

ADIPOSE TISSUE
- fat breakdown

URINARY SYSTEM
- Decreased urine output

REPRODUCTIVE SYSTEM
-male sexual response

49
Q

What is the importance of the ADRENAL MEDULLA?

A

Adrenal medulla is an adrenal exocrine gland above the kidneys
- it enhances the timing and intensity if the SNS response

SNS pre-ganglionic neurons target the adrenal medulla , which releases (through diffuse spread) EPINEPHRINE & NOREPINEPHRINE as hormones into the bloodstream
- Epi and NorEpi effects enhances and reinforces ALL SNS targets

Adrenal CORTEX: steroid hormones [endocrine system]

note :innervated by SNS pre-ganglionic neurons (no Post-ganglionic neurons)

50
Q

Parasympathetic functions & when is it dominant ?

A

aka “rest and digest”
Dominant when body is quiet
(what does the body need to replenish)

> CONSERVE ENERGY
-decreased heat rate
-decreased force of contractions of heart
-constrict airways

> INCREASED DIGESTION
-Increased mucus, saliva and digestive secretions
-Increased digestive motility ans relax sphincters

> ADJUST FOR NEAR VISION
- constrict pupils

51
Q

What structures does the Parasympathetic NS target to be able to serve these functions ?

A

CARDIOVASCULAR SYSTEM
- Decreased heart rate, heart contraction, bloodpressure

RESPIRATORY SYSTEM
- Decreased airflow

SALIVATORY GLANDS
-Increased secretion

DIGESTIVE SYSTEM
- Increased activity & motility
- Increased secretion
- Increased nutrient storage

52
Q

discuss the difference between dual and single innervation

A

DUAL INNERVATION
-Most organs are involved by both SNS and PSNS (aka the “accelerator” & “breaks”)
> SNS vs PSNS COMPETITION
– Has a Baseline tone of input , just like somatic NS
– Baseline SNS and PSNS different for each organ
=> Activity of one (frequency of action potentials) will increase to overcome the other based on behavioural need

SINGLE INNERVATION
- there are some exceptions to dual innervation
[exceptions]= innervated only by SNS neurons
How? –> regulated by increasing/ decreasing action potential rate from SNS only

(examples)

> LIVER: SNS only

> ADIPOSE TISSUE: SNS only

> BLOODVESSELS: SNS only

> SWEAT GLANDS: SNS only but the SNS post-ganglionic terminals release ACETYLCHOLINE

53
Q

Explain sympathetic regulation ito bloodvessels

A

Increased sympathetic activity CONSTRICTS blood vessels
- aka electrical signal from neurons increase

Decreased sympathetic activity DILATES blood vessels
- aka electrical signal from neurons decrease

54
Q

ORGAN LEVEL RECEPTORS
How many NTs are responsible for all the SNS and PSNS changes at the organs?

A

ONLY TWO

Differences in organ responses, then, are mainly due to specialization of RECEPTORS in each organ

55
Q

Last few slides are summarised lols

A

physiology 214 (1 decks)

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