L1 anatomy Flashcards
What forms the central nervous system (CNS)?
The brain together with the spinal cord and the cranial nerves
What does the central nervous system control?
Both conscious and unconscious functions of your body
What did the “Treatise of Man” by Rene Descartes say about nerves?
Nerves are hypothesized to be conductors of information from the skin and sense organs to the brain and back from the brain to the muscles
What has the central nervous system evolve into?
A device made of nerve cells that processes information to convert sensory input into appropriate motor output
Which part of central nervous system is oldest?
Spinal cord
How does the spinal cord takes in information?
From sensory neurons from the dorsal nerve roots and sends information back out through nerves at the ventral roots
What will happen if there is a sudden tap on the patellar tendon?
The quadriceps muscle will be stretched
What is sensory stretch receptor neurons’ name in patella reflex?
Dorsal root ganglion cells
Where does the sensory stretch receptor neurons connect to in patellar reflex? And what is their effect?
Motor neurons in the ventral horn of the spinal cord. The motor neurons will cause the quadriceps muscle to contract
What innervates the hamstrings to relax in patellar reflex?
Inhibitory interneurons in the ventral horn
What is the other name for simple neural circuit?
Monosynaptic
What does patellar reflex help with?
Postural adjustment
Name a complex reflex.
Withdrawal reflex
Name a neural control structure.
Central pattern generators which produce rhythmic locomotive movement
What is the general pattern of organization that is applicable to reflex arcs and brain? (input and output)
Sensory information enters the CNS at the back and motor outputs are computed and sent out to the front
What are afferents?
Nerve cells which carry information toward higher processing centres
What are efferents?
Nerve cells which carry signals toward motor output structures
How the brain has evolved?
By layering more and more complex input-output loops on top of existing ones
How did Charles Sherrington imagined all brain function?
Potentially huge complex, interlinked and hierarchically organized reflex arcs that interact
What did the brain researchers think Sherrington’s view underestimated?
The importance of innate drives and long term memories in shaping perception and motivation
Name the multiple circuits that serve visual purpose.
Older: Superior colliculus (optic tectum)
Newer: Visual cortex
Name the multiple circuits that make people move.
Spinal chord reflex arcs and cerebellar and motor cortical circuits
Are the multiple circuits active in parallel?
Yes
What are brain’s circuits made of? And how many of them in one human brain?
Nerve cells (neurons). 100billion.
Neurons differ greatly in…
Shape and size
On average neuron cell bodies are roughly…across (how many microns)
20 microns
What is the only output cable?
Axons
Use of axons.
Signals are transmitted along axons using electrical signals
Use of synapses.
Use chemical signals to transmit the information on to another neuron/ a muscle fibre/ gland
What is the main input cable and what does it do?
Dendrites and receive chemical signals from many other neurons
What does the nucleus contain of?
Cell body (Soma)
Axons can project __distance.
Long
What does the axon of one neuron typically contact with?
The dendrites or somata of many others
What is the connections between axons and dendrites?
Synapses
What is the chemical switch?
Synapses
What do neurotransmitters in synapses do?
Control the opening of ion channels, and allow electrical currents to flow into or out of the receiving cell
Synaptic currents from how many are integrated to determine the voltage?
10,000 synapses
Which part determines the voltage?
Axon hillock
What do the voltage determine?
The rate of ‘nerve impulses’ (action potentials) sent down the axon to other neurons
The connection strength of the synapses between neurons can be plastic, allowing…
Allows the neural network to learn new ‘associations’ between the pieces of information represented by the activity of individual neurons.
What is artificial neural network inspired by?
Brain research and led to breakthroughs in artificial intelligence
How many neurons are there in a brain?
100 billion
Do you have millions more neurons in your gut or in your spinal cord?
Spinal cord
What do neurons on average do?
Receives and sends out thousands of ‘synaptic connections’
Number of synapse in the brain.
10^15. Hence, tens of thousands of times larger than the number of seconds that you can expect to live (3*10^9)
Are there more glial cells or more neurons in nervous system?
More glial cells
Do glial carry sensory or motor signals themselves?
No.
What do astrocytes do?
Important for the metabolic regulation of the nervous system
What do oligodendrocytes & Schwann cells do?
Provide myelin sheath surrounding axons
What do microglia do?
Involved in immunological reactions to damage in the nervous system
What does gray matter contain?
Nerve cell bodies (neurons)
What does white matter contain?
Axons (nerve fibres)
What is decussation?
The crossing point of nerve tracts that input and output pathways to and from the brain is crossed.
Examples for decussations.
Optic chiasm, ‘decussation of the pyramids’ in the cortico-spinal tract
The brain is a ____plane.
Mid-sagital
What is the use of pineal gland?
Secretes hormones, e.g., melatonin, which makes you sleepy at night
What are commissures?
Fibre bundles connecting one brain hemisphere to another
What is the part connecting the two hemispheres of the cerebral cortex
Corpus callosum
What is Rostral?
Toward face
What is Caudal?
Toward the tail
What is Ventral?
Toward the belly
What is Medial?
Toward the midline
What is Lateral?
Toward the side
What is Inferior?
Lower, below
What is the three-layered skin covering the CNS?
Meninges
Name the three layers of meninges.
Dura mater (hard), arachnoid (spiderous), pia mater (soft)
What is meningitis?
When meninges become infected and inflamed.
p.s. usually bacterial disease (meningiococcus) can be very serious.
What does the arachnoid do?
Reabsorbs cerebro-spinal fluid generated in the brain’s ventricles
What are ventricles?
Cavities in the brain that are filled with cerebro-spinal fluid
Where are cerebro-spinal fluid secreted from?
Choroid plexus
Blockage of cerebro-spinal fluid circulation through the ventricles will lead to?
Severe swelling of the ventricles, known as hydrocephalus (water head)
Do brain capillaries have pores?
No
How does the exchange of substances between brain and blood work?
Actively regulated by carrier proteins produced and controlled by astrocytes
The exchange of substances between brain and blood ensures what?
Levels of substances abundant in food (salts, amino acids) can’t change rapidly depending on what and when you eat. Keeps drugs and poisons out of brain.
What can be diffused through the blood-brain barrier?
Fat soluble substances, including alcohol or cannabis
What do the frontal lobe do?
Movement, cognition
What do the parietal lobe do?
Touch, spatial orientation and attention
What do the occipital lobe do?
Vision
What do the temporal lobe do?
Hearing, object recognition, memory
What are gyri and sulci in human cortex?
Prominent ridges and grooves
How thick are the sheet of nerve cells of cortex
2mm
The sheet of nerve cells covers how big?
2500 cm2
Each mm3 of the cortical sheet contains how many neurons?
100,000
Total number of cortical neurons.
50 billion
How many different areas delineated on Brodmann areas?
52
What did the Brodmann areas base on?
Cytoarchitectonic differences of different regions of cortex
What do the Brodmann areas correlate well with?
Functional specializations identified
What are area 1-3?
Primary somatosensory cortex
What is area 17?
Primary visual cortex
Name the layers of Brodmann areas in sequence.
- Molecular 2. External granular 3. External pyramidal 4. Internal granular 5. Internal pyramidal 6. Polymorphous
Which area has a prominent layer 4?
Area 17 (visual cortex)
Which area almost has no layer 4?
Area 4 (primary motor cortex)
Where are cortex sensory areas found?
In the posterior half
What do the anterior half cortex do?
Motor control and decision making
Which part is an obligatory relay between sensory input and cortex?
Thalamus
What does obligatory relay between sensory input and cortex mean?
Sensory afferents from all the sense synapses (except smell) in thalamus and thalamic neurons connect to cortex
Why does cortex send nerve fibres back down to thalamus?
To send signals of expectation or selective attention to thalamic relay neurons, so that thalamus only sends the most relevant information to cortex
Thalamic activity is important in…
Mediating sleep and in directing attention
What does hypo mean?
Below
What does hypothalamus control?
Appetite, thirst, blood pressure, body temperature, sleep-wake (circadian) rhythms, the regulation of the levels of growth hormones, stress hormones and sex hormones
What is pituitary?
Hormone secreting gland
Describe the pathway of pituitary gland.
Connected to the hypothalamus via pituitary stalk and the hypothalamus directly controls it’s function
What does pituitary gland do?
Gets inputs from the hypothalamus to control hormone levels involved in functions as diverse reproduction, growth, thirst or stress levels
What is ganglia/ nuclei?
Clumps of neurons
Describe the feedback circuit of basal ganglia.
Starts in frontal and prefrontal parts of cortex and pass through the basal ganglia to thalamus and back to cortex
Name the parts of basal ganglia.
Striatum: Caudate and Putamen, the Globus Pallidus, the Subthalamic Nucleus and the Substantia Nigra
What does the basal ganglia do?
Action selection, habits and addiction
What does cerebellum do?
Motor control
How does the cerebellum operate?
Receives diverse sensory inputs from all over the brain and is thought to learn to associate that with motor output patterns in order to make motor execution ‘smooth’ and automatic after practice
Damage in cerebellum will lead to?
Slower and clumsier movements (ataxia and apraxia), disturbed balance
What is hotly debated about the cerebellum?
Its role in cognition and emotion
What the latin word for ‘edge’?
Limbus (eng: limbic)
Name the key members of the limbic system.
Amygdala, hypothalamus, thalamus, hippocampus and cingulate cortex
Limbic structures are old or new?
Old
What is the limbic system responsible for?
Emotional responses, e.g., fear, anger and arousal
What does the nervous system control?
Muscles and glands
Name a new structure and its job.
Neocortex which is enormous in humans and is critical in analytical or creative thinking or language
Describe the brain parts.
Symmetric, hemispheric pairs and richly interconnected by fibre bundles
