KNOW THESE BETTER Flashcards
Metencephalon - made up of what 2 brain structures?
- Pons: houses many fibre tracts and part of reticular formation
- Cerebellum: 50% of all neurons in the brain; Massively connected to cortex – multiple cerebro- cerebellar systems; Involved in movement and timing
Mesencephalon (midbrain) - composed of:
the tectum (“roof”), which contains nuclei that receive and relay:
- visual information (superior colliculi)
- auditory information (inferior colliculi)
the tegmentum (“floor”), which contains nuclei related to:
- motor function (substantia nigra and red nucleus)
- pain (periaqueductal grey)
Structure that can span across multiple sections
Reticular formation
Reticular formation
- midbrain, pons, medulla
- Reticulum means “little net”
- In the myel-, met- and mesencephalon (midbrain + hindbrain)
- Many nuclei that play roles in arousal, attention, cardiac and respiratory reflexes, and other jobs
Diencephalon - composed of…
- thalamus
- hypothalamus
Diencephalon - Thalamus
- 2-lobed structure
- Different types of nuclei – some process and relay info between receptors and cortex
- **Nuclei may be specific to one sense or combine information from many senses (EX: if someone suddenly threw a frisbee, you would both be able to SEE it and HEAR it)
- Thalamus & cortex are closely connected
Thalamo-cortical loops and consciousness
- Thalamus and cortex are closely connected - important in how we see the world as a unified place
- General anesthetics tend to act upon the nonspecific nuclei of the thalamus (as well as other structures)
- Abnormal synchronization in the thalamo-cortical network can cause absence (“ab-sonce”) seizures
The hypothalamus
- Hypo = under, hence, UNDER the thalamus in the brain
- Plays an important role in behaviours such as feeding, sex, sleeping, temperature, emotion, and movement
- Acts upon the body’s endocrine (hormone) system via the pituitary gland (instructs the endocrine system)
Telencephalon involves which 3 structures
- Basal ganglia
- Limbic system
- Cerebral cortex
Basal Ganglia
- “Lower knots”
- Collection of nuclei highly connected to cortex, thalamus, and midbrain
- Involved in movement and learning
Limbic system - made up of what 2 structures (amongst other structures):
- Hippocampus (“seahorse”) – plays a role in spatial memory
- Amygdala (“almond”) – plays a role in emotion
Cerebral cortex - Sulci and Gyrus
Sulci deep enough to indent the ventricles are also called fissures
- Sulcus: bottom of wrinkle
- Gyrus: top of wrinkle
Is the cortex just one layer?
NO - made of up to 6!
Cerebral cortex - 90% of the human cerebral cortex is…
isocortex (sometimes called neocortex) = 6-layered
Cerebral cortex - 10% of the human cerebral cortex is…
- …allocortex = <6 layers
- Hippocampus, olfactory (piriform) cortex
What is the role of the meninges?
Three layers of membranes known as meninges protect the brain and spinal cord
What 3 layers make up the meninges?
- The delicate inner layer: pia mater.
- The middle layerz; the arachnoid, a web-like structure filled with fluid that cushions the brain
- The tough outer layer: the dura mater.
- ANATOMY: NEURONS -
Does AP occur anywhere along the axon?
- Unmyelinated axons have Na+ channels (Nav) all along their surface
- Myelinated axons not all covered by myelin; rather, have little bubbles and gaps between myelinated areas, leaving the axon exposed
- Nav only at the nodes of Ranvier: where myelin is interrupted
The synapse - receiving…
- postsynaptic neuron
- Postsynaptic neurons have a variety of receptors that fit, like a lock and key, with specific neurotransmitters
- When NTs bind to a corresponding receptor, they trigger changes that push the charge of the postsynaptic cell up (towards depolarizing) or down (towards hyperpolarizing)
Neurotransmitters can be (3 types)
- Excitatory: make the receiving neuron more likely to fire an action potential
- Inhibitory: make the receiving neuron less likely to fire an action potential
- Modulatory: trigger other changes
Neurotransmitter cleanup
- Diffuse away
- Broken down by enzymes
- Reuptake
○ By presynaptic neuron
○ By glia
Reuptake inhibitors
- Serotonin (5-HT) & norepinephrine (=noradrenaline) are neurotransmitters
- These drugs are generally used to treat depression, anxiety, and pain
Other cell in the nervous system
- Glia
- “glue,” “sticky”
- 10x more numerous than neurons
4 subtypes of glia
- Oligodendroglia
- Schwann cells
- Microglia
- Astroglia
Oligodendroglia
wrap around the axons of neurons in CNS, forming many myelin sheaths per cell
Schwann cells
wrap around the axons of neurons in PNS, forming one myelin sheath per cell
Microglia
- (smallest type of glial cell) respond to injury & disease, engulfing debris and triggering immune response
- Only in CNS
Astroglia
are the largest glial cells:
- Support endothelial cells of the BBB
- Provide nutrients to neurons
- Maintain ion balance in CNS
- Repair after injury
- Communicate with neurons and glia
- Control and maintain synapses
Only in CNS
Which of the 4 subtypes of glial cells is in the PNS?
Schwann cells
NEUROLOGICAL EXAM
3.Motor Function - Key features to examine:
- Gross appearance of muscle
- Muscle tone, strength
- Strength: how much force can a muscle exert, when you’re trying to exert force
- Muscle tone: how active is a muscle at rest
Upper motor neurons originate in _ or _ and use _
motor cortex, brainstem; glutamate
Upper motor neuron lesions can lead to
- Weakness
- Spasticity - Muscle “catches”; ridgity
- Hyperreflexia
- Retained primitive reflexes (e.g., grasp, suck, snout)
Lower motor neurons originate in _ or _ , _ , and use _ (incl. motor cranial nerves)
spinal cord or brainstem, innervate muscles or glands, and use acetylcholine
Lower motor neuron lesions can lead to:
- Weakness
- Hypotonia (low tone)
- Hyporeflexia
- Atrophy
- Fasciculations: fine movements of the muscles under the skin
4.Somatosensory
Somatosensory Function
- Temperature
- Pain
- Vibration
- Proprioception
- Touch
Somatosensory - issues with touch
- Astereognosis = inability to recognize objects by touch
- (Subtype) Agraphesthesia = inability to recognize letters/numbers by touch
- > both point to sensory cortex of parietal lobe
5.Coordination - Quick, alternating movements can test
- Dysmetria > impairment performing accurate movements
- EX: putting the cap on a pen
5.Coordination - Romberg’s test
- balance with eyes open vs closed
- +ve Romberg points to cerebellar damage
5.Coordination - Pronator drift
Pronator drift = rotation and vertical motion of arm
- EX: in the neurological exam video - when eyes are closed, hands held out either rotate (pronates) or one raised above the other
- Points to damage to the pyramidal tract (efferent fibres from cortex to brainstem or spinal cord)
