Synapses and brain Flashcards
What did Camillo Golgi do and think
Camillo Golgi (1890): silver chromate salt to reveal the intricate structures of a single neuron. Thought that the nervous system was like the circulatory system, with a branching system of tubes, one unit, not multiple.
what did Santiago Ramón y Cajal think
Santiago Ramón y Cajal: (used Golgi’s method), hypothesized that the functional unit of the brain is the neuron, also known as the ‘neuron doctrine’.
why do neurons have polarity
Neurons have polarity, they go in a direction. Information is collected at one point, then transmitted to another point
what is the Soup vs Spark debat
Soup vs Spark debat:
- Soup - chemicals are used for inter neuron transmission
- Spark - electricity is used for inter neuron transmission
What did Loewi discover
Loewi’s Results
- Electrical stimulation of the vagus nerve attached to heart #1 caused heart #1 to slow don
- After a delay, heart #2 also slowed down
- Loewi hypothesized that electrical stimulation of the vagus nerve released a chemical into the fluid of chamber #1 that flowed into chamber #2
- He called this chemical “Vagusstoff”
- We now know this chemical as the neurotransmitter acetylcholine
what are neuropeptides
Several neuropeptides, relatively short chains of amino acids, also function as neurotransmitters
Neuropeptides include substance P and endorphins, which both affect our perception of pain
what do Opiates do
Opiates bind to the same receptors as endorphins and can be used as painkillers
what do gases do
Gases such as nitric oxide (NO) and carbon monoxide (CO) are local regulators in the PNS
CO/NO are not stored in cytoplasmic vesicles, but is synthesized on demand (note: inhaling CO can be deadly, the vertebrate body synthesizes small amounts of it)
what is a chemical synapse
The presynaptic neuron synthesizes and packages the neurotransmitter in synaptic vesicles located in the synaptic terminal
(most neurons only make one type of neurotransmitters, other make multiple)
The action potential causes the activation of Ca2+ channels
Ca2+ entry triggers fusion of vesicles
The neurotransmitter diffuses across the synaptic cleft and is received by the postsynaptic cell
what are PSPs
- Direct synaptic transmission involves binding of neurotransmitters to ligand-gated ion channels in the postsynaptic cell
- Neurotransmitter binding causes ion channels to open, generating a postsynaptic potentials (PSPs)
- Postsynaptic potentials fall into categories
- Excitatory postsynaptic potentials (EPSPs) are depolarizations that bring the membrane potential toward threshold
- Inhibitory postsynaptic potentials (IPSPs) are hyper-polarizations that move the membrane potential farther from threshold
how are neurotransmitters clear
- Diffusion
- enzymatic hydrolysis
- recapture of neurotransmitters by transporters
can a single neurotransmitter bind to only one receptor
- A single neurotransmitter may bind specifically to more than a dozen different receptors, triggering their activation
- A neurotransmitter can excite postsynaptic cells expressing one receptor and inhibit postsynaptic cells expressing a different receptor
What are Ionotropic receptors and Metabotropic receptors
- Ionotropic receptors gate ion flow
- Metabotropic receptors are G-protein couples receptors
- Binding of a neurotransmitter to a metabotropic receptor activates a signal transduction pathway in the postsynaptic cell involving a second messengers (e.g. cAMP, PKC)
- Compared to ligand-gated channels, the effects of second-messenger systems have a slower onset but last longer
what are the four different types of synapse
At electrical synapses, the electrical current flows from one neuron to another through gap junctions
At chemical synapses a neurotransmitter carries information between neurons
Mixed synapses have both
Heterosynaptic interactions involved both types of axon leading into the same cell, and interact with each other
is a single EPSP enough to start an AP
Single EPSP is usually too small to trigger an action potential in a postsynaptic neuron
If two EPsPs are produced in rapid succession, an effect called temporal summation occurs. Which might be enough to start an action potential
what are EPSPs
Excitatory postsynaptic potentials (EPSPs) are depolarizations that bring the membrane potential toward threshold
Driven by excitatory receptors with equilibrium potentials close to 0 mV
what are IPSPs
Inhibitory postsynaptic potentials (IPSPs) are often hyper polarization that move the membrane potential farther from threshold
Driven by inhibitory receptors with equilibrium potentials around -60 to -90 mV
how are EPSPs and IPSPs spatially summed
In spatial summation, EPSPs produced nearly simultaneously by different synapses on same postsynaptic neuron add together
The combination of EPSPs through spatial and temporal summation can trigger an action potential
Through summation, an IPSP can counter the effect of an EPSP
The summed effect of EPSPs and IPSPs determines whether an axon hillock will reach threshold and generate and action potential
what do Glia do
Glia cells, or glia have numerous functions to nourish, support, and regulate neurons; 10 to 50x more than neurons in a given area!
Embryonic radial glia form tracks along which newly formed neurons migrate
Astrocytes induce cells lining capillaries in the CNS to form tight junctions, resulting in a blood-brain barrier (BBB) and restricting entry of most substances into the brain
what type of nervous system did the simples animals have
By the time of the Cambrian explosion more than 500 million years ago, specialized systems of neurons have appeared that enable animals to sense their environment and respond rapidly
The simples animals with nervous systems, cnidarians, have neurons arranged in nerve nets, a series of nerve cells weakly interconnected via gap junctions
what did bilaterally symmetrical animals develop
- Bilaterally symmetrical animals exhibit encephalization, the clustering of sensory organs at the front end of the body
- Relatively simple cephalized animals, such as flatworms, have a central nervous system (CNS)
- The CNS consists of a brain and longitudinal nerve cords
- The peripheral nervous system (PNS) consists of neurons carrying information in and out of the CNS
what kind of nervous system do Annelids and Arthropods have
Are segmentally arranged clusters of neurons called ganglia
have a brain, ventral nerve cord, and segmental ganglia
what type of nervous system do cephalopods have
Most advanced of invertebrates
Have a brain, and two ganglia
Distributed along whole body
Similar amount of neurons to a cat
what kind of nervous system do vertebrates have
In vertebrates
- The CNS is composed of the brain and spinal cord
- The PNS is composed of nerves and ganglia
Spinal cord holds the dorsal nerve cord
Sensory ganglia along dorsal nerve cord
what does the spinal cord do
The spinal cord conveys information to and from the brain and generate basic patterns of locomotion
The spinal cord also produced reflexes independently of the brain
A reflex is the body’s automatic response to a stimulus
what does the knee jerk reflex do
Sensory afferents excite muscles on which they sense stretch, causing contraction
They also inhibit and relax antagonistic muscle using an inhibitory interneuron
describe the PNS
The PNS transmits information to and from the CNS
Afferent neurons transmit information to the CNS and efferent neurons transmit information away
two efferent components: the moto system and autonomic nervous system
Motor system: voluntary skeletal muscles
The autonomic nervous system: generally involuntary
what does the sympathetic NS do
The sympathetic NS regulates arousal and energy generation (fight or flight response). A paired chain of ganglia that runs alongside the spinal column, extending from the cervical to the coccygeal level
what does the parasympathetic NS do
The parasympathetic NS has antagonistic effects on target organs and promotes calming and a return to “rest and digest” functions
what does the Enteric NS do
Enteric NS: incredibly sophisticated, 100 million neurons. Controls motility of the digestive tract, and secretion from pancreas, and gallbladder.
What effect does the Parasympathetic division do
Parasympathetic division: Constricts pupil of eye, stimulates salivary gland secretion, constricts bronchi in lungs, slows heart, stimulates activity of stomach and intestines, stimulates activity of pancreas, stimulates activity of pancreas, simulates gallbladder, promotes emptying of bladder, promotes erection of genitalia
what does the sympathetic division do
Sympathetic division: Dilates pupil, inhibits salivary gland secretion, relaxes bronchi in lungs, Accelerates heart, inhibits activity of stomach and intestines, inhibits activity of pancreas, stimulates glucose release from liver, inhibits gallbladder, stimulates adrenal medulla, inhibits emptying of bladder, promotes ejaculation and vaginal contractions
what are the regions of the vertebrate brain
Forebrain: has activities including processing of olfactory input, regulation of sleep, learning, and any complex processing
Midbrain: coordinates routing of sensory input
Hindbrain: controls involuntary activities and coordinates motor activities
How does each part of the brain develop
Forebrain splits into Telencephalon (Cerebrum (includes cerebral cortex, white matter, basal nuclei) and Diencephalon (which includes the thalamus, hypothalamus, and epithalamus)
The Midbrain leads to the Mesencephalon which is part of the brain stem
The hindbrain leads to the Metencephalon (pons (part of the brainstem) and cerebellum) and the Myelencephalon (medulla oblongata (part of brain stem))
What is the Telencephalon
Right and left cerebral hemispheres connected via the corpus callosum
Cerebral cortex is vital for perception, motion, and higher-order functions
Deep within the white matter are clusters of nuclei, the basal nuclei which are involved in moto planning
what is grey vs white matter
The brain and spinal cord contain
- Gray matter; neuron cells bodies, dendrites, and unmyelinated axons
- White matter: Myelinated axons
what does the CNS develop from
The CNS develops from the hollow nerve cord, which gives rise to the narrow central canal of the spinal cord and the ventricles of the brain
what is cerebrospinal fluid
The Canal and 4 ventricles fill with cerebrospinal fluid filtered from blood and functions to cushion the brain and spinal cord to provide nutrients and remove wastes
what is the cerebral cortex
The cerebrum, the largest structure in the human brain is essential for awareness, language, cognition, memory, and consciousness
Four regions or loves (frontal, temporal, occipital, and parietal), are landmarks for particular functions
what are the functions of the frontal lobe
Frontal lobe damage may impair decision making and emotional responses but leave intellect and memory intact
The frontal lobes have a substantial effect on “executive functions”
Gage was an American railroad foreman known for having survived a traumatic brain injury caused by an iron rod that shot through his skull and obliterated the greater part of the left frontal lobe of his brain. Remarkably he recovered all his senses but his character changed
what is Broca’s area
Broca’s area in frontal lobe is active when speech is generated– Patients with damage in this are can understand language, but cannot speak*
what is Wernicke’s area
Wernicke’s area (posterior temporal lobe) is active when speech is heard– Damage to this area causes patients to be unable to understand language, though they can still speakBW
what is lateralization
This right and left hemispheres of the brain show difference in function called lateralization
Music songs gets split: on the left side you can decode the speech content, and on the right side you can only decode the melodic content (but not the speech content)
what is the left hemisphere better at
Left hemisphere is also more adept at math and logical operations
The left side of the cerebrum has a greater role in language that the right side
what is the right hemisphere better at
In contrast the right hemisphere appears to dominate in the recognition of faces and patterns, spatial relationships, and nonverbal thinking
What’s up with the Diencephalon
In between
Thalamus, relay centre for most sensory information
Hypothalamus: Homeostasis and Hormones
- Thermoreceptive neurons in heat loss centre (vasodilation/sweating) and heat gain centre (shivering) work to maintain body at 37º C
- Release Oxytocin/Vasopressin (anti-diuretic hormone) into posterior pituitary glands (”master gland”); also control hormone release from anterior pituitary (growth hormone, thyroid stimulating hormone, FSH/LH, Adrenocorticotropic hormone; ACTH: HPA stress axis
- Regulate appetite (hunger and satiety centres)
- Circadian rhythms are coordinated by a group of neurons in the hypothalamys called the suprachiasmatic nucleus (SCN). SCN is a pacemaker (~24), synchronizing the biological clockPineal: release melatonin, which plays an important function in maintaining diurnal rhythms; capillaries form CSF
What’s up with the Mesencephalon
The Mesencephalon (mid)
- Tectum (ceiling): Superior and Inferior colliculi - sensory motor integration
- Tegmentum (floor)
- Substantia Nigra: major source of DA to the basal nuclei; required for initiating movements; degeneration leads to Parkinson’s disease
- Ventral Tegmental Area (VTA): mesolimbic DA (nucleus acumbmens) reward; mesocortical projections
- Periaquiductal gray (PAG): gate pain signals, rich in opioid receptors
- Red nucleus: rhythmic movement, gait
What happens with Parkinson’s Disease
Substantia Nigra: major source of DA to the basal nuclei; required for initiating movements; degeneration leads to Parkinson’s disease
What’s up with the Metencephalon
The Metencephalon (back)
- Pons
- Lots of tracts to cerebral and cerebellar hemispheres
- Raphe nucleus: major source of serotonin (5HT) in the brain; controls respiration centres in the medulla oblongata; aggression; mood; major target for anti-depressants (selective Serotonin Reuptake Inhibitors; SSRIs) and sleep
- Locus coerules: major source of norepinephrine (NE) in the brain; involved in arousal, alertness and attention - Cerebellum: motor coordination; learned motor tasks
What’s up with the Myencephalon
The Myencephalon (bottom)
- medulla Oblongata: respiration and heart rate
- Baroreceptors located in the heart muscles, aorta and carotid arteries (supply blood to the brain) and provide blood pressure information to the medulla → SA node)
