Synapses, Neurotransmitters, Hormones Flashcards
What is synaptic transmission?
How neurones communicate with each other
What is a synapse?
The gap between neurones where signals are passed from one to another
What are the two types of synapses?
Electrical and chemical
What are the characteristics of an electric synapse?
Small gap between two neurones (2-4nm), large channels to allow ions to move directly from one neurone to another, process is similar to propagation of an action potential, fast, prevalence in PNS due to muscle contraction
How are action potential propagated in electric synapses?
From the pre-synaptic neurone to the post-synaptic neurone
What are the characteristics of a chemical synapse?
Specialised structures to transmit chemical signals, larger gap (20-40nm), slow transmission, high prevalence in neurones (1000)
What is the process in chemical synapses with action potential?
- Action potential arrives at pre-synaptic membran3
- VG Ca 2+ channels open
- Ca 2+ diffuses into the cell
- Synaptic vesicles fuse with the membrane
- Neurotransmitters released into the synaptic cleft
- Neurotransmitter binds to the postsynaptic receptor, opening the ion channels
What is the fusion process of vesicles?
Lipid membrane forms a large opening for release into the cleft
What is the criteria for neurotransmitters?
Must be synthesised in the pre-synaptic neurone, present in the axon terminal and released in a calcium dependant manner upon depolarisation of the pre-synaptic neurone
What do amino acid transmitters do?
Fast transmission such as glutamate with the related amino acid aspartate
What are examples of biogenic amines?
Noradrenaline, adrenaline, dopamine
How are biogenic amines produced?
By the amino acid tyrosine and then decarboxylation occurs
How do neuropeptides work?
They have long term neuromodulatory effects due to interaction with metabotropics
What are the three groups of neuromodulator peptides
Enkephalins, endorphins, dynorphins
What is a property of enkephalins?
Pain relieve
What are properties of endorphins and dynorphins?
Pain relief and euphoria
What happens if the synapse is excitatory?
NA + channels open, depolarisation occurs leading to an excitatory postsynaptic potential (EPSP)
What happen if the synapse is inhibitory?
Cl- channels open, hyperpolarisation occurs leading to an inhibitory postsynaptic potential (IPSP)
What are receptors?
Membrane proteins that bind neurotransmitters in a lock and key principle so each receptor type can bind only to a specific neurotransmitter
What are ionotropic receptors?
Receptors that lead to the opening or closing of an ion channel so there is a change in the ion channel permeability for a flow of ions across the cell membrane
What are ionotropic receptors responsible for?
Fast, brief and precise synaptic transmission
What is the structure of an ionotropic receptor?
Ligang-gated ion channel, receptor site is apart of the ion channel protein
What are metabotropic receptors?
Receptors where the binding of neurotransmitters activates a G protein
What does a G protein do?
Bind to an ion channel which will influence opening or closing or activate secondary messengers
What do metabotropic receptors allow?
Slower and prolonged signalling
What are neurotransmitters?
A chemical released that will transmit signals between neurones
What are characteristics of neurotransmitters?
Synthesised in the pre-synaptic neurones, localised to vesicles in the pre-synaptic neurone, released from the pre-synaptic neurones, removed by the synaptic cleft, binds to receptor
What happens to neurotransmitters when the signal is transmitted?
It is either recycled in the cleft by reuptakers or neutralised by enzymes
What are 4 excitatory neurotransmitters?
Acetylcholine, glutamate, norepinephrine, serotonin
What is acetylcholine’s role?
Muscle control
What is glutamate’s main role?
Learning and memory
What is norpinephrine’s main role?
Fight or flight response and arousal
What is serotonin’s main role?
Mood, appetite, sensory perception
What are 2 inhibitory neurotransmitters?
Dopamine and GABA
What is dopamine’s main role?
Reward, motivation, movement
What is GABA’s main role?
Calmness and relaxation
How do SSRIs work?
Blocking the reuptake so serotonin can bind to nerve cells
What is a neuromodulatory system?
A set of neural networks and at the core a small number of neurones in the brainstem
How are neurotransmitters secreted?
By a small group of neurones in large areas of the nervous system
What is the noradrenergic locus coeruleus involved with?
Regulation of attention, arousal, learning, memory, anxiety, pain, mood
What are the two parts of the serotonergic raphe nuclei?
Caudal nuclei and rostral nuclei
How does the caudal nuclei work?
Innervate the spinal cord for pain related sensation
How does the rostral nuclei work?
Innervares the brain for the sleep wake cycle and regulation of the sleep stages
What is the serotoneric raphe nuclei implicated in?
Control of mood and emotions
What is the cholinergic basal forebrain involved with?
Arousal, sleep wake cycle, learning and memory
How do neurones project in the dopaminergic substantia nigra?
From the substantia nigra to the striatum to control voluntary movement
How does the ventral tegmental area project in the dopaminergic substantia nigra?
To the frontal cortex areas of the limbic system for reward system
What is dopamine involved in?
The reward system associated with pleasure and euphoria increasing the odds that we will repeat the activity
What happens after a period of use for dopamine?
Tolerance and a decrease in dopamine receptors
What are hormones?
Molecules secreted by endocrine glands that travel in the bloodstream to influence organs or glands
What are the features of hormonal communication?
Long lasting effects, produced in small amounts, interaction with other hormones, influence behaviours, many affect different body parts
What is the endocrine system?
The glands of the body where hormones are produced
What does the endocrime system help?
Regulation of organs, maintaining of homeostasis
Where is the hypothalamus located?
Below the thalamus forming the walls of the third ventricle
How is the hypothalamus divided?
Into several nuclei that have specific functions
Where is the pituitary gland?
Connected to the base of the hypothalamus
What are the three zones of the hypothalamus?
Lateral, medial and periventricular
What part of the hypothalamus is the most connected to the pituitary?
The periventricular
What does the hypothalamus control?
Circadian rhythms and organs via the autonomic nervous system
What does the hypothalamus integrate?
The somatic and visceral responses in accordance with the needs of the brain
What is homeostasis?
The maintaining of the body’s internal environment in a narrow physiologic range such as temperature, pH and oxygen levels
What does the pituitary gland do?
Production of many hormones to stimulate other glands to produce hormones
What are the pituitary gland two divisions?
Posterior and anterior
How is the posterior pituitary gland connected?
To the hypothalamus
Where are neuro-hormones produced?
In the magnocellular hypothalamus which is release at the pituitary
What is the posterior PG main hormone release?
Oxytocin and vasopressin
What does oxytocin do?
Uterine contractions and lactation
What is oxytocin triggered by?
Somatic, visual or auditory stimuli
What does vasopressin do?
Stimulate ADH
How is vasopressin regulated?
By blood volume and pressure
What hormones are implicated in forming romantic attachments
Oxytocin and vasopressin
How is oxytocin released? (Romantic formation)
In response to social bonding and physical intimacy
What does the release of oxytocin cause? (Romantic formation)
Feelings of trust, closeness, emotional bonding
What is vasopressin linked with? (Romantic formation)
Pair bonding and attachment in humans
How does vasopressin influence people? (Romantic formation)
A person’s preference for a specific partner and the commitment to a relationship
What does vasopressin contribute to? (Romantic formation)
The maintenance of a long term relationship
How is the anterior pituitary gland connected?
To the pituitary
What do parvocellular neurosecretory cells release?
Tropic actors to cause the production of hormones
What are examples of hormones produced from tropic actors?
ACTH (adrenal cortex control), FSH (growth of ovary follicles/sperm), growth hormone (growth of cells), LH (increase in testosterone)
What is the main stress response system?
Hypothalamic-pituitary-adrenal axis
What is the process where hormones effect stress?
- Hypothalamus releases CRH in response to stress.
- In response to CRH, the pituitary releases ACTH
- ACTH stimulates the adrenal glands, in response to ACTH the adrenal glands release cortisol into the bloodstream
- Cortisol prepares the body for the stressor by increasing energy production and suppressing non essential functions
- Cortisol provides negative feedback to the hypothalamus and pituitary to stop releasing CRH and ACTH
What is the signals, pathways, speed of information, duration of effect, type of action and response and the target for the nervous system?
Electrical (action potentials)
Transmission by neurones
Fast
Short-lived
Voluntary or involuntary
Localised (to cells connected to neurones)
What is the signals, pathways, speed of information, duration of effect, type of action and response and the target for the endocrine system?
Chemical (hormones)
Transported by the blood
Slow
Short or long-lived
Involuntary
Distant (many cells can be effected)
