Neuroanatomy: Synopsis and revision Flashcards
What does the Forebrain/Prosencephalon primary vesicles develop into ?
The forebrain (prosencephalon) develops into the Telencephalon and the Diencephalon.
The Telencephalon becomes the cerebral hemispheres in the adult and the cavities of it becomes the lateral ventricles.
The Diencephalon becomes the Thalamus and its cavities become the third ventricle
What does the Midbrain/Mesencephalon primary vesicles develop into ?
The Midbrain (Mesencephalon) stays as the Mesencephalon and becomes the Midbrain in the adult and the cavities of it becomes the cerebral aqueduct
What does the Hindbrain/Rhombencephalon primary vesicles develop into ?
The hindbrain (rhombencephalon) develops into the Metencephalon and the Myelencephalon.
The Metencephalon becomes the pons and cerebellum in the adult and the cavities of it becomes the upper part of the fourth ventricle.
The Myelencephalon becomes the Medulla and its cavities become the lower part of the fourth ventricle
What are the different parts of the CNS?
- CNS; Encephalon + Spinal Cord
- Encephalon (Brain); Cerebrum + Brain stem + Cerebellum
- Cerebrum; Telencephalon (Cortex + white matter + basal nuclei - grey matter) + diencephalon
Brainstem; - Midbrain + Pons + Medulla
Name all of the cerebral lobes
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Insula
Limbic lobe (debate whether this one exists or is a border)
How do we know the functions of each lobe?
By studying the relation between lesions and the change caused in patient
Animal Experiments
Functional imaging techniques (PET, fMRI - looks at brain blood movement) helped us understand the functions of different regions of the nervous system
What is the function of the frontal lobe?
The frontal lobe is responsible for ;
Voluntary muscle movement;
- Primary motor cortex
- Premotor cortex
Language production;
- Front operculum in dominant hemisphere (90% people dominant in left) - Broca’s area
Higher cognitive functions (impulse control, decision-making, problem solving, social interaction, attention)
- prefrontal cortex
What is the function of the parietal lobe?
The parietal lobe is responsible for;
Integration of somatosensory information
- Primary and secondary somatosensory cortices
Movement
- Primary Somatosensory cortex
Language
- Wernickle’s area (partially) in the dominant hemisphere
Reading
What is the function of the temporal lobe?
The temporal lobe is responsible for;
Conscious memory
- Medial temporal lobe esp. Hippocampus and neighbouring cortices
Auditory processing
- Auditory cortices
Comprehension of speech
- Wernicke’s area (primarily)
Olfaction
- Medial temporal lobe, temporal pole
What is the function of the occipital lobe?
The occipital lobe is responsible for;
Visual perception and processing
Memory
What is the function of the insula?
The insula is responsible for;
Olfaction
Taste
Discriminative touch
What is the function of the limbic lobe?
The limbic lobe (means frame) is responsible for;
Behavioural and emotional responses
Learning and memory
What is the uncus and its significance ?
The uncus is the innermost part of the temporal lobe and receives its name from its hook-shaped structure. Anatomically, the anterior segment of the uncus overlies the amygdala and belongs to the parahippocampal gyrus
The uncus can turn into an uncal herniation which can lead to death
What is in the diencephalon?
Made up of the Thalamus and Hypothalamus
What is the function of the Thalamus?
The Thalamus is the major relay station for;
- Sensory impulses ascending to sensory cortex (except smell)
- Inputs from subcortical motor nuclei and cerebellum travelling to the cerebral motor cortex
What is the function of the Hypothalamus?
The Hypothalamus is the major relay station for;
- Autonomic control
- Endocrine control (w/pituitary gland)
- Regulation of thirst -> fluid electrolyte balance
- Eating -> energy balance
- Sexual behaviour, reproduction
- Body temperature
How does the pituitary gland (hypophysis) develop ?
It develops in part from diencephalon called Neurohypophysis and a part from the roof of the mouth (the anterior lobe) called the adenohypophysis
They are attached to hypothalamus so functions are closely related to the hypothalamus
How is the neurohypophysis formed and what does it do?
The Neurohypophysis is formed by the median eminence, pituitary stalk and posterior lobe of the hypophyseal gland
The neurohypophysis secretes 2 hormones that are produced in the hypothalamus (produced in hormone precursors higher up called paraventricular nucleus and the supraoptic nucleus).
How is the adenohypophysis formed and what does it do?
The adenohypophysis produces and secrets hormones of its own into the hypophyseal portal system
What is in the midbrain and their functions?
The midbrain contains superior and inferior colliculi and they are the visual and auditory reflex centres respectively
Red nuclei containing the subcortical motor centre
Substantia nigra is involved in reward-seeking, motor caring and others
The red nucleus and substantial nigra and parts of the basal nuclei (not basal ganglia as that is in PNS! - same structures and function, different location)
What is the basal nuclei + ganglia
Masses of grey matter embedded and surrounded by white matter
What is the function of the pons?
The pons is the conduction area between forebrain and cerebellum
Nuclei contribute to regulation of respiration as well a hearing and balance
What is the function of the medulla?
It is where pyramidal decussation occurs (crossing of corticospinal axons) before entering spinal cord
vital centres regulating; respiratory rhythm, heart rate, blood pressure
Non-vitals centres regulating; cough, sneeze, swallowing and vomiting
Fun fact!: Area postrema is here which is a chemo receptor target zone - makes vomit
Where are the respiratory centres and how do they function?
Thy are found in the medulla and pons
Dorsal respiratory group (DRG) responsible for INSPIRATION
- establishes the rhythm of normal quiet inspiratory breathing
- Neurons in DRG stimulate nerves t the diaphragm and external intercostals muscles
- If DRG is completely suppressed breathing stops (overdose, sleeping pills, alcohol, etc).
Ventral Respiratory group (VRG) - EXPIRATION
What is the reticular formation and how is it formed?
The reticular formation is all of the neural networks that are formed from the cranial nerves.
The polysnaptic network in the brainstem, surrounding principal sensory & motor nuclei and tracts
Continues rostrally into the thalamus and hypothalamus, and caudally into the spinal cord (to modulate pain and affect muscle tone)
Input and output to virtually all parts of the CNS but connectivity is extremely complex
Divided into 3 longitudinal zones, and 5 columns which use different neurotransmitters
What are the parts of the reticular formation and what do these do?
The reticular formation;
Median articular formation (raphe nuclei)
- sleep
- pain
Paramedian reticular formation (gigantocllular reticular nuclei)
- Sensory pathways
- Muscle tone
Lateral reticular formation (parvocellular reticular nuclei)
- All of these sensory pathways, including the special senses
- Cranial nerve reflexes and visceral functions
What does the reticular formation control?
State of consciousness; sleep and wakefulness (coma or vegetative state)
Pattern generation (essential to life)
- Cardiovascular control
- Regulation of respiratory cycle
Pattern generation (not essential to life)
- Conjugate eye movement
- Gait
Swallowing, vomiting, coughing and sneezing
Control of micturition
Nociception and pain modulation
What is the ascending reticular formation and descending reticular formation and their functions?
Ascending reticular formation is SENSORY; contains reticular activating system (RAS) which;
- Awakens the cerebral cortex from sleep
- Maintains consciousness/attention
- Filters incoming stimuli to discriminate irrelevant background stimuli
- Pain modulations
Descending reticular formation is MOTOR;
- helps maintain muscle tone (balance and posture)
If someone is in a coma or vegetative state what isn’t working?
Their ascending reticular formation as it should be waking the up e.g - Archie Battersbee
What is the cerebellum and its functions?
The cerebellum is made up of 2 hemispheres in cerebellar fossa
Connected to brain stem by cerebellar peduncles (superior, middle, inferior)
Processes and interprets impulses from motor cortex and sensory pathways and coordinated motor activity for smooth, well-timed movements - important for balance
What are the different type of neurons?
Unipolar - we don’t have just animals
Bipolar - found in our ears
Pseudounipolar - adults have these
Multipopar neurons;
- Motor neuron
- Pyramidal neuron
- Purkinje cell
What are the functional classifications of neurons?
Afferent neuron; Neurons, axons of which many carry information to the CNS
Efferent Neuron;
Neurons, axons of which carry impulses towards the end organ
- Upper motor neurons; a motor neurons, including its axon whose cell body is in the cerebral cortex and goes down the spinal cord to synapse
- Lower motor neurons; a motor neurons, including its axon whose cell body is in the ventral horn of th spinal cord or motor nucleus in the brain stem
What are the 7 modalities (from medial to lateral) of different neurons?
7 modalities (from medial to lateral);
1). General somatic efferent (GSE) to striated voluntary muscles
2). Special visceral efferent (SVE) to muscles from pharyngeal arches
3). General visceral efferent (GVE) to smooth muscles, glands (sympathetic and parasympathetic)
4). General visceral afferent (GVA) - General sensation
5). Special visceral afferent (SVA) for olfaction and taste
6). General somatic afferent (GSA) for perception of pain, touch and temperature
7). Special somatic afferent (SSA) for vision, hearing and balance
How are neurons organised from the spinal cord to the brainstem?
In the spinal cord grey mattress more vertical
The grey matter starts to open up dorsally the higher up you go
In the brainstem the grey matter is found more horizontal
Through out all of this the nuclei order remains the same
How does myelination look in the CNS and PNS?
Dendrites are always unmyelinated, just some axon myelinated
Unmyelinated axons have a covering - extensions of cytoplasm covers and oligodendrocytes can cover more than 1 axon
In the PNS its the same but Schwann cells cover axons in myelin, however only one Schwann cell can myelinated 1 axon where as oligodendrocytes can do many
What are some of the main neuroglia and their function?
PNS;
Satellite cells - Surround neuron cell bodies in ganglia; regulate O2, CO2, nutrient and neurotransmitter levels around neurons in ganglia
Schwann Cells - Surround all axons in PNS; responsible for myelination of peripheral axons; participate in repair process after injury
CNS;
Ependymal cells - Line ventricles (brain) and central canal (spinal cord) assist in producing, circulating and monitoring of CSF
Oligodendrocytes - Myelinate CNS axons; provide structural framework
Astrocytes - Maintain BBB, provide structural support, regulating ion, nutrient and dissolved gas concentrations; absorb and recycled neurotransmitters; from scar tissue injury
Microglia - remove cell debris, wastes and pathogens by phagocytosis
What directions do the white matter tracts of the brain travel?
- Up/down; Projection fibres (internal capsule)
- Front/back; Association fibres (superior longitudinal fasciculus)
- Left/right; Commissural fibres (corpus callous, posterior commissure)
What are the features of upper and lower motor neurons?
Upper motor neurons (presynaptic);
- Neuron bodies in the cortex
- Most of the axons cross over in the lower medulla
- Descend in the lateral column of spinal cord as lateral corticospinal tract
- Synapse with LMN in the anterior horn
Lower motor neuron (postsynaptic);
- Neuron bodies in anterior horn
What features would you expect to see in an upper motor neuron lesion?
- Hypertonisa (spasticity)
- Hyper-reflexia
- Abnormal reflex (Positive Babinski sign unless younger than 6 months old)
What features would you expect to see in an lower motor neuron lesion?
- Hypotonia/flaccidity
- Hypo-reflexia/areflexia
- Fasciculations
- Atrophy/wasting of muscles
How is the spinal cord organised?
Into Grey matter - Horns containing;
Central canal
Neuron cell bodies
- Dorsal/posterior horns -> cell bodies of interneurons
- Lateral horns -> visceral (autonomic) motor cell bodies (T1-L2 segments)
- Ventral/anterior horns -> somatic motor cell bodies
White Matter - Columns with Ascending and descending tracts: Paired and most decussate;
- Ventral (anterior) columns
- Lateral Columns
- Dorsal (posterior) columns
What do peripheral nerves do?
Links CNS to peripheral tissue
What are some facts about the spinal nerves?
There are 7 cervical vertebrae but 8 spinal nerves (1 above, 1 below)
C1 nerve;
- Passes about C1 vertebra
- Motor only; no sensory fibres
C8 nerve passes between C7 and T1 vertebrae
Spinal cord ends between L1/2 -> where would do a lumbar puncture
Caudal equina - what happens when vertebral canal is narrowed below L2 - Causes lumbar spinal stenosis
How does the spinal nerve take sensory stimulation and act upon it?
The sensory information is passed along the spinal nerve by th posterior, synapses with the dorsal root ganglion which passes the information into the dorsal horn of the spinal cord. The spinal cord processes and passes this information out of th ventral horn where a motor root takes in to the skeletal muscles and also feeds back motor sensory information to where thee sensation was initially picked up. There is also an anterior and ventral root which synapses at the sympathetic ganglion and is a communication branch to both the organ and sensory area. (IDK IF THIS IS RIGHT?)
What is on of the main causes of spinal nerve injury?
Slipped disc
What are the protective layers of the spinal cord?
Vertebral canal
Epidural fat
Dura matter
Arachnoid matter
Pia matter
Subarachnoid space with CSF
How is the spinal cord supplied with blood?
We have paired posterior spinal arteries;
- from the vertebral artery of the posterior inferior cerebellar artery
Single anterior spinal artery;
- formed from a contributory branch from each vertebral artery
Aorta -> intercostal arteries -> radicular arteries reinforce anterior and posterior spinal arteries
The great anterior medullary artery of Adamkiewicz arises from the aorta in the lowers thoracic or upper lumbar vertebral levels
- it may be the major source of blood to the lower 2/3rds of the spinal cord
How is the spinal cord drained of blood?
Internal vertebral venous plus (anterior and posterior)
- Lies in the epidural/extradural space (between the dura and the vertebrae)
- Do not have valves and pressure gradients permit blood flow
- Communicates with cranial dural venous sinuses and pelvic veins -> spread of infection and metastasis
What is the nerve supply to the spinal cord like?
Spinal nerves join with others to form plexus except thoracic nerves?
Some of the muscles in and part of the cervical region area supplied by the cervical plexus
What does the ANS do?
Its distributed in the whole body
Sympathetic system;
- cell bodies in lateral horn of T1-L2 segments
- Postganglionic cell bodies lie in paravertebral sympathetic ganglia
- Ganglia interconnected -> sympathetic chain
Paraysmpathetic system
- Cell bodies in brainstem and S2-4 segments
How does the sympathetic system head and neck work?
The spinal nerves travel up the chain to synapse in the cervical ganglion
Postganglionic axons pass in the GRC and join cervical spinal nerves
How does the sympathetic system in the rest of the spinal cord wok?
Each sympathetic trunk (chain) extends between atlas and coccyx
Number of paravertebral sympathetic ganglia < number fo vertebrae
- Superior (C1-4), middle (C5-6) and inferior (C7-8) cervical ganglia
- If inferior cervical + T1 -> Steellate ganglion (cervicothoracic ganglion) (C7 - T1)
How does CSF drain?
Lateral ventricles drain through intraventricular foramina into the third ventricle which drains through the cerebral aqueduct into the fourth ventricle which drains through lateral and median aperatures into the subarachnoid space which drains into thee arachnoid villi of dural venous sinuses into the venous blood which goes to the heart and lungs.
CSF is made in all of the ventricles by their choroid plexuses (e.g lateral ventricles choroid plexus) and does this by using arterial blood
What are the different neurons in nerves and receptors and their features/functions ?
Two autonomic neurons;
Presynaptic neuron
Synapse;
- receptor - usually nicotinic
- Neurotransmitter - Acetylcholin
Postsynaptic;
- Receptors; muscarinic, adrenergic
- Neurotransmitters;
Aceetylcholin, noradrenalin
