4. Neurotransmitters, Neuronal Communication & Hormones Flashcards
How large is the gap between two neurons in electrical synapses?
2-4nm
How large is the gap between two neurons in chemical synapses?
20-40nm
Ionotropic receptors control the ion channel…
Directly
When bound with the transmitter the ion channels open and… (ionotropic receptors)
Ions flow across the membrane
What are ionotropic receptors also known as?
Ligand-gated ion channels
What do metabotropic receptors activate?
G-proteins that subsequently control the ion channel
What are the 6 properties of neurotransmitters?
- Synthesized in the presynaptic neurone
- Localised to vesicles in the presynaptic neuron
- Released from the presynaptic neurone under physiological conditions
- Rapidly removed from the synaptic cleft by uptake or degradation
- Presence of receptor on the post synaptic neurone
- Binding to the receptor elicits a biological response
What is the role of Acetylcholine?
A neurotransmitter used by the spinal cord neurons to control muscles and by many neurons in the brain to regulate memory
What is the role of dopamine?
The neurotransmitter that produces feelings of pleasure when released by the brain reward system. Dopamine has multiple functions depending on where in the brain it acts
What is the role of GABA?
The major inhibitory neurotransmitter in the brain
What is the role of glutamate?
The most common excitatory neurotransmitter in the brain
What is the role of glycine?
A neurotransmitter used mainly by neurons in the spinal cord
What is the role of Norepinephrine?
In the PNS, it is part of the fight-or-flight response. In the brain, it acts as a neurotransmitter regulating normal brain processes
What is the role of serotonin?
Involved in many functions including mood, appetite and sensory perception
Continued presence of neurotransmitters in the synaptic cleft would lead to persistent…
EPSPs or IPSPs - even without further APs in the presynaptic neuron
To prevent a continuing firing of EPSPs/IPSPs due to presence of neurotransmitters, they are either…
- Moved back into the pre-synaptic neurone (through reuptake)
- Degraded/neutralised by enzymes
What is the purpose of point-to-point communication?
Restricts synaptic communication
What is the purpose of hormonal communication?
Secretes chemicals into the blood stream to affect the entire body
What is the purpose of interconnected neurons of the ANS?
Simultaneously controls responses in many internal organs
What is the purpose of diffuse modulatory systems?
Specific neurotransmitters regulate arousal, mood, motivation, sexual behaviour, emotion, sleep etc.
Messages that must be widely broadcast through the brain use what kind of system?
Diffuse modulatory
Diffuse modulatory systems each require a specific…
Neurotransmitter
The connections of diffuse modulatory systems are widely dispersed throughout where?
The brain
What are diffuse modulatory systems important for?
Motor control, memory, mood, motivation and metabolic state
What kind of disorders are diffuse modulatory systems heavily involved in?
Psychiatric
The core of each diffuse modulatory system has a small number of what?
Neurons
Neurons of the diffuse system arise from where?
The core of that system
Where are the diffuse modulatory systems located?
In the brain stem
Describe how neurotransmitters are released throughout DMS?
They are released into extracellular fluid and can diffuse to many different neurons
Modulatory systems affect wide areas to make them more or less…
Excitable or synchronously active
DSM can influence the whole…
Cortex
Projections, in terms of DSM, are..?
Links between cells
What is the Noradrenergic Locus Coeruleus?
The Norepinephrine system
The Norepinephrine system makes some of the most diffuse…
Connections in the brain
The norepinephrine system is involved in the regulation of what?
Attention, arousal, sleep-wake cycles, learning and memory, anxiety, pain, mood and brain metabolism
What is the Norepinephrine system active by?
New, unexpected, non-painful sensory stimuli
What is the Serotonergic Raphe Nuclei?
The serotonin system
The serotonin system is made up of what?
The Caudal innervate spinal cord and the rostral innervate brain
What does the serotonin system modulate?
Pain-related sensation
When does the Rostral innervate brain fire most and why?
During wakefulness as it is part of the reticular activating system
What is the Rostral innervate brain mostly involved in?
Sleep-wake cycles and stages of sleep & the control of mood and emotional behaviours
The Caudal Nuclei projects into where and is responsible for what?
Into the spinal cord and is responsible for pain
Serotonin is very important when concerning what type of issues (give an example)?
Mental health issues such as depression
The Cholinergic Basal Forebrain is also known. as what?
The Acetylcholine system
The general function of which system is not completely understood?
The Cholinergic Basal Forebrain
The Cholinergic Basal Forebrain is implicated in what?
Arousal, sleep-wake cycles, learning and memory
Which disease causes the degeneration of cells within the cholinergic basal forebrain?
Alzheimer’s
The Dopaminergic Substantia Nigra is known as what?
The Dopamine System
In the dopamine system, the neurons project from where to where?
Substantia Nigra to the striatum
What does the dopamine system control?
Voluntary movements
The degeneration of the dopamine system results in what disease?
Parkinson’s
The ventral tegmental area projects to where from where?
To the frontal Cortex to the limbic system
The reward system reinforces what (from the dopamine system)?
Adaptive behaviour
Some types of depression are believed to be due to a lack of what neurotransmitter?
Serotonin
What is the name of treatment of depression involving serotonin?
SSRIs (selective serotonin rue-take inhibitors)
Describe how SSRIs are used to treat symptoms of depression
They work by increasing the amount of serotonin that bind to postsynaptic receptors
The SSRIs block the rue-take of serotonin and therefore increasing the number of serotonin left in the synaptic cleft
Describe how antagonistic drugs work
Drugs that block the effects of neurotransmitters
Give 2 examples of antagonistic drugs
Novacaine and caffeine
Describe how agonist drugs work
Drugs that mimic or increase the effects of neurotransmitters
Give 3 examples of agonist drugs
Heroine, LSD and cocaine
Almost all abused drugs stimulate the release of what in where?
Stimulate dopamine release in the nucleus accumbens
Describe the nucleus accumbens
A groups of cells located in the frontal lobe and is related to the feelings of pleasure
Describe the two ways in which ‘meth’ alters dopamine transmission
- Enters dopamine vesicles in axon terminal causing release of transmitter
- Blocks dopamine transporters from re-uptaking dopamine
How does meth result in feelings of euphoria?
Results in more dopamine in the synaptic cleft & therefore neurones fire more often
How can meth cause issue with the brain?
We usually see less activity in their nucleus accumbens
LSD is which type of hallucinogen?
Serotoninergic hallucinogen
Describe the physical effects of LSD
Dilated pupils, higher or lower body temp, sweating or chills, sleeplessness, dry mouth, tremors
Describe the mental effects of LSD
Delusions, visual hallucinations, an artificial sense of euphoria or certainty, distortion of one’s sense of time and identity, severe terrifying thoughts and feelings, fear of losing control, panic attacks, flashbacks, severe depression or psychosis
What does Alcohol alter within the brain?
Alters neuronal membranes - ion channels, enzymes and receptors
What receptors does alcohol bind to?
Acetylcholine, serotonin, GABA, glutamate
Define hormones
Chemicals secreted by one cell group travel through blood to targets
Where are hormones released from
Endocrine glands
How many general principles of hormones are there
9
What are principles 1-3 of hormones?
- Gradual, often, long-lasting effect
- Change likelihood of behaviour
- Hormones and behaviour interact
What are principles 4-6 of hormones?
- Many different hormones affect many different body parts and behaviours
- Produced in small amounts (often in small bursts)
- Many have rhythmic release
What are principles 7-9 of hormones?
- Hormones interact with other hormones
- All vertebrate hormones have similar structures, but not necessarily similar effects
- Can only affect cells with the appropriate receptor proteins
Hormones travel through the blood and influence the activity of what?
Other glands and hormones
Hormones produce what types of changes in where?
Short and long-term changes in various cells and organs
What type of neurotransmitters are hormones similar to?
Neurotransmitters at metabotropic receptors
A hormone can only influence cells that…
Have specific target receptors for that particular hormone
The secreting cell does what?
Secretes hormones into blood vessels
How do hormones travel to their target cell?
Through the blood
What are two types of hormones?
Protein and steroid
Describe the features of protein hormones
Comprised of amino acids
Protein and amine hormones faster than steroids
Bind to receptor, activate second messenger
Second messenger alters cell function
Describe the features of steroid hormones
These are derived from cholesterol from the diet
Bind directly to membrane receptors
Much slower
Affect the long term production of proteins within the target cells
All glands of the body and hormones are produced by what system?
The endocrine system
What is the endocrine system very important for?
Homestasis
Where is the hypothalamus located and which ventricle does it form the walls of?
Below the thalamus and forms the walls of the third ventricle
What is the pituitary connected to?
The base of the hypothalamus
The hypothalamus integrates which type of responses?
Somatic and visceral responses in accordance with the needs of the brain
Define homeostasis
Ensuring the body has a balanced internal environment
What are the 3 zones of the hypothalamus?
Lateral, medial and periventricular
Which zone of the hypothalamus is most highly connected to the pituitary?
The periventricular
The periventricular controls what?
Circadian rhythms and ANS to viscera
The posterior pituitary gland is connected to what?
The hypothalamus
Where are neuro-hormones produced and released?
Produced in the magnocellular hypothalamus and released at the pituitary
What does the release of oxytocin initiate?
Uterine contraction or milk-let down
What triggers the release of oxytocin?
Somatic, visual or auditory stimuli or inhibited by stress
Describe vasopressin and what it does
Antidiuretic hormone which regulated blood volume and pressure
What is the anterior pituitary gland connected with?
The hypothalamus
What do parvocellular neurosecretory cells release?
Tropic factors that cause the production of hormones in the anterior pituitary
What does ACTH do?
Controls the adrenal cortex (kidneys)
What does TSH do?
Controls the release of thyroid hormones
What does FSH do?
Controls growth of ovary follicles/sperm
What does prolactin do?
Promoted milk production
What does LH do?
Promotes rupture of follicles/increase in testosterone
What does growth hormone do?
Promotes growth of cells/tissues
What is oxytocin involved in and what does it stimulate?
Involved in reproductive and social behaviour by stimulating contractions
The Pineal Gland is activated by which nervous system?
The sympathetic nervous system
Which hormone does the pineal gland release at night?
Melatonin
Which gland influences puberty and reproductive condition?
The Pineal Gland
In humans, which rhythm is impacted by the pineal gland?
Sleep rhythms
