Week 1-Brain structure and function Flashcards
Define Biopsychology
the scientific study of the biology of behaviour with a biological approach to psychology AND denotes (indicates) the biological drivers of thought and behaviour. (also known as psychobiology OR behavioural neurosciences)
Define Neuroanatomy
The study of the nervous system structure (basis of this week’s notes)
Define Neurophysiology
The study of the functions + activities of the nervous system (basis of this week’s notes)
Define Neurochemistry
The study of the chemical basis of neural activity
Define Neuroendocrinology
The study of interactions between the nervous system and the endocrine system.
Define Neuropathology
The study of nervous system disorders
Define Neuropharmacology
The study of the effects of drugs on neural activity (neuro=nerves)
What is the brain and what does it allow us to achieve?
■A complex pinkish-grey mass of tissue that weighs about 1.5kg
■Houses the mind of a human being – memories, thoughts and emotions. Wishes, aspirations, disappointments – the capability of consciousness, self-reflection and free will.
■Enabled us to be dominant creatures on earth – artistic, scientific, medical and technological achievements
Why are we able to achieve what we can because of the brain?
This is because of the complexity of our brains:
-100 billion neurons (lecture 2)
-Each projecting to 5000-10,000 other neurons (i.e., literally trillions of connections – synapses)
How does brain research benefit us all?
It allows us to understand human afflictions (e.g., mental illness, degenerative disease) to try and improve treatment
History: What did Plato (429-348 BC), Ancient Greece propose?
The brain is the organ of reasoning (previously believed to be the heart)
History: What did Galen (AD 130-200), a physician of the Roman Empire propose?
proposed a theory that brain function is based on ventricles – not allowed to perform human dissection in Rome (body seen as sacred), so observed cattle and oxon
When were the first drawings of the brain drawn?
Late 15th century (drawn by Leonardo da Vinci)
Who is René Descartes (1596-1650) and what did he propose?
A French Philosopher and mathematician – he thought, therefore he was “Cognito; ergo sum” (I think therefore I am)
Proposed that mind and body interacted in the pineal gland. Also realised much behaviour was mechanical, not requiring mental processing
Developed the concept of the automatic reflex – the basis of our modern understanding of sensory nerves conveying messages to the brain
Importantly some behaviour is reflexive – the mind is not involved (although it feels pain, and is aware of what happened) but NOT A CAUSE of behaviour e.g., moving hand away from a candle
Descartes paved the way for the scientific and non-secular approach to understanding human physiology (religious or spiritual matters)
How many Nobel peace prizes have been awarded in neuroscience?
50
What does the central nervous system divide into?
- brain
- spinal cord
How does the peripheral nervous system divide?
- autonomic nervous system (communicates with internal organs and glands):
-sympathetic division (arousing)
-parasympathetic division (calming) - somatic nervous system (communicates with sense organs and voluntary muscles):
-sensory (afferent aka enter) nervous system (sensory input)
-motor (efferent aka exit) nervous system (motor input)
What are the sensory organs?
eyes, ears, nose, tongue, and skin
True or false: Both ANS and SNS contain afferent and efferent nerves + give an example in the SNS
True, Example:
*Sensory (afferent) nerve senses hot flame on the skin (external sense organ). Afferents sense the heat and send rapid messages to the spinal cord – conveying the message of heat pain!
*Motor (efferent) nerves respond by sending signals from CNS to muscles, to move the hand away from the flame
What’s the ANS?
Some motor actions are involuntary and “automatic” e.g., heart and breathing (we don’t have to consciously think about these)
What’s the SNS?
Controls the voluntary movements part e.g., moving your hand away from the flame.
How many types of efferent nerves does the ANS have?
2 (Projecting from the CNS to internal organs)
What’s the Sympathetic nervous system?
Autonomic motor nerves that prepare us for action (fight or flight)
*Think of this as responding to a stressor (a lion) e.g., heart rate increases
*MOBILISES energy
What’s the Parasympathetic nervous system?
Autonomic motor nerves that prepare us to relax
*Your peaceful restful state e.g., increases digestion
*CONSERVES energy
What are directional terms in neuroanatomy?
*Terms for a 3D coordinate system to help neuroanatomists explain and navigate where something is in the brain
*These are described in relation to the orientation of the neuraxis (which is the direction in which the CNS lies in relation to the spinal cord)
What’s bipedalism?
The fact you’re standing on two feet (means the brain isn’t in a straight line with the spinal cord)
Directional terms: Name the 3 axes used in animals
1.Anterior-posterior
2.Dorsal-ventral
3.Medial-lateral
Define dorsal and ventral in animals
D-Toward the back of the body,
or towards the top of the head
V-Toward the front (belly) of the
body or towards the bottom of the head
Define rostral and caudal in animals
R-Toward the front end of the body (nose)
C-Towards the tail
Define medial and lateral in animals
Medial = toward the midline
Lateral = away from the midline
Define dorsal and ventral in humans
D: Toward the back of the body, or towards the top of the head (because of right angle neuraxis)
V: Towards the front (belly) of the body or towards the bottom of the head
Define rostral and caudal
R: Towards the nose
C: Towards the feet (humans) or tail
Define proximal and distal
Proximal = close to CNS e.g. shoulders
Distal = far (distant) from CNS e.g. fingers
Define Bilateral/ Ipsilateral/Contralateral
■ Bilateral: On both sides of the
body or head
■ Ipsilateral: On the same side of the body or head
■ Contralateral: On the opposite side of the body or head
True or false: Directional terms can combine
True e.g., Ventromedial (towards the bottom of the head towards the midline), Dorsolateral, Ventrolateral, Dorsomedial
Directional terms: Define horizontal, coronal and saggital
H: just horizontal
C: cut from front to back like a slice
S: cut like an apple in half
Directional terms: Define cross-section
A slice taken at right angles to
the neuraxis.
Define Midsaggital plane
the plane through the neuraxis perpendicular to the ground; divides the brain into 2 symmetrical halves.
What’s Meninges and how does it protect the brain?
-different protective membranes
*For obvious reasons the brain and spinal cord are well protected by bone and 3 protective membranes (membrane = selective barrier, which allows some things to pass but not others)
*Dura mata
*Arachnoid membrane
*Subarachnoid space (between arachnoid and pia mater where CBF passes through)
-Meningitis
What’s Cerebrospinal Fluid and how does it protect the brain?
*Fluid that fills the subarachnoid space, the spinal cord and ventricles of the brain
*CBF provides cushioning and support for the brain.
*People who have this drained suffer headaches and pain because their sensitive brains are not protected by the fluid.
*Excess CBF is continually absorbed into subarachnoid space and sinuses which run through dura mata and drains into the jugular vein
*If obstructed (e.g., a tumour between ventricles) CBF can build up in ventricles leading to brain expansion. A condition called hydrocephalus (water head)
What’s the blood-brain barrier and how does it protect the brain?
*A semi-permeable membrane, which separates blood from the CBF, providing a barrier that prevents many toxins from entering the brain from the bloodstream (using endothelial cells)
*The degree to which therapeutic or recreational drugs (psychoactive drugs) work, depends on the ease with which they can cross the BBB
What 5 divisions/major structures of the brain are evident in from embryonic development to adulthood?
1.Myelencephalon –medulla - largely comprises tracts between the brain and spinal cord. (Covered in myelin which is white insulated matter on the neurons hence the name)
2.Metencephalon - pons and cerebellum.
3.Mesencephalon - tectum and tegmentum.
4.Diencephalon – thalamus and hypothalamus.
5.Telencephalon – cerebral cortex, limbic system and basal ganglia.
What’s the Myelencephalon (Medulla)?
*Part of the hindbrain – most posterior part of the brain (brain stem)
*Oldest part = medulla oblongata (long marrow) – controls breathing, heart rate, salivation, vomiting
*If brain is cut above the medulla basic heart rate and breathing are maintained. Damage to medulla = fatal
*Contains the reticular formation (involved in sleep, attention movement, and cardiac, circulatory and respiratory reflexes)
What’s the Metencephalon?
- Part of the hindbrain – most posterior part of the brain
- Contains pons and cerebellum
- Pons (bridge) – enlargement of medulla, contains pontine nuclei – contains coeruleus and dorsal raphe = origin of noradrenergic and serotonergic containing fibrers in the forebrain
- Cerebellum (little brain) important for sensorimotor control – control of movements
- Cerebellum damage can cause problems with decision-making and language too
What’s the Mesencephalon (midbrain)?
*Part of the midbrain –two divisions (tectum and tegmentum)
*Tectum: dorsal of midbrain. Inferior colliculi (auditory function), superior colliculi (visual-motor function)
*Tegmentum: contains PAG– Primary control centre for descending pain modulation (contains enkephalins which are an endogenous neurochemical which binds to opioid receptors)
Endogenous=produced within us
*Substantia nigra – important component of the sensory-motor system
What’s the Diencephalon (forebrain)?
*Up to this point brain could be likened to a tube that has evolved and enlarged from the spinal cord. Forebrain mushrooms out from so that it covers and surrounds the
older ‘tubular’ brain, and adds greater complexity and new structures – e.g., hypothalamus and thalamus
* Thalamus (Greek: inner chamber) – relays sensory signals from skin to prepare motor signals to the cerebral cortex. Also involved in sleep, consciousness, alertness
* Hypothalamus – important for motivated behaviours (eating, sleeping and sexual behaviour)
What’s the Telencephalon?
- Everything else! Mediates most of the brain’s complex functions – voluntary movement, sensory input, cognitive processes – learning, speaking, problem-solving
- Contains cerebral cortex AND subcortical structures – as well as important fibre bundles
Telencephalon: What’s the Cerebral Cortex?
*Composed of small unmyelinated neurons
*Grey matter (other layers are composed of large myelinated axons and are white matter)
*Convolutions (dips in the brain) serve to increase surface area
*Large convolutions = fissures
*Small convolutions = sulci
*Ridges between fissures and sulci = gyri
*Longitudinal fissure separates hemispheres (it remains connected by cerebral commissure, inc corpus callosum)
*Contains the NEOCORTEX, and subcortical structures (hippocampus, limbic system, basal ganglia)
Subcortical structures – What’s the hippocampus?
*Has 3 major layers
*Located at the medial edge of the cerebral cortex, folds back on itself in the medial temporal lobe
* Hippocampus means seahorse
*Has a major role in memory (spatial location memory)
Subcortical Structures – What’s the limbic system?
■Limbic system – circuit of midline structures that circle the thalamus
■ regulation of motivated behaviours and consists of mammillary bodies,
hippocampus, amygdala, fornix, cingulate, septum
Subcortical Structures – What’s the Basal ganglia?
- Motor system.
- Consists of amygdala, striatum (caudate nucleus + putamen), globus pallidus
- Extrapyramidal motor system (output fibres do not cross the pyramidal regions of the medulla)
- Degeneration of the nigral-striatal pathway causes rigidity, tremor and slow movement in Parkinson’s disease
- Involved in the coordination of automated (without thinking) smooth, fluent movement.
Why has the neocortex got its name?
- It is the newest part of the cerebral cortex to evolve
- Cerebral cortex = largest part of telencephalon, composed of grey matter. Neocortex = largest part of cerebral cortex (90% of cerebral cortex is neocortex in humans). Other part is allocortex (contains hippocampus) I.e., subcortical structures
What is the main difference with the neocortex?
- Main difference is that neocortex has six layers – the most developed in its number of layers and organisation of the cerebral tissues (specific to mammals)
- Humans have large neocortex ratio, which correlates with complexity of behaviour. For a large neocortex to evolve, the brain must evolve in size to support it
- Central and lateral fissure divide each hemisphere into 4 lobes (frontal, parietal, temporal and occipital)
- lobes are not functional units
What are the 4 lobes of the cerebral cortex/neocortex and their functions?
- frontal lobe: motor cortex (precentral gyrus) and complex cognitive functions (frontal cortex)
- temporal lobe: hearing, language, complex visual patterns and memory
- occipital lobe: visual processing
- parietal lobe: somatic sensations e.g., touch (postcentral gyrus) and orientation (location of objects)
Explain the case of HM and the amnesic effects of bilateral medial temporal lobectomy
An epileptic who had his temporal lobes removed in 1953 (27 years old)
In 11 years preceding surgery averaged one generalised seizure p/w, and several focal seizures per day (despite anticonvulsants)
His generalised seizures stopped, and partial seizures reduced massively. Left surgery well-adjusted, normal perceptual and motor ability, normal intelligence…Memories for events predating surgery intact (more or less), short term memory pretty good too.
BUT…total inability to form new long-term memories. In effect, H.M became suspended in time that day in 1953, when he regained his health, but lost his future
What did EEGs previously suggest about seizures?
EEG suggested seizures arose from foci in both left and right temporal lobes. Removal of one medial temporal lobe had proved effective in patients with unilateral temporal lobe focus – thus a decision was made to remove medial portions of both temporal lobes inc hippocampus, amygdala
Explain the case of Phineas Gage: neuroscience’s most famous patient
13 sept 1848 (25 years old) Gage began tamping before sand. The tamping iron struck a rock, causing a spark to light the powder the explosion propelled his tamping iron through his head.
Entered under his left cheekbone, penetrated base of skull behind left eye socket, emerged at the top of the skull
Despite his horrific injury, within minutes Gage was sitting up in a cart, conscious and recounting what had happened
In 1868 Harlow wrote a report on the ‘mental manifestations’ of Gage’s injuries. He described Gage as “fitful, irreverent, indulging at times in the grossest profanity… capricious and vacillating” and being “radically changed, so decidedly that his friends and acquaintances said he was ‘no longer Gage’.”
The damage to Gage’s frontal cortex resulted in a loss of social inhibitions. Gage’s injuries provided some of the first evidence that the frontal cortex was involved in personality and behaviour.
What is the primary goal of psychobiologists?
To use this knowledge of brain anatomy (from the level of cellular architecture to distinct structures and regions and how they interact and connect with one another) to improve our understanding
of BRAIN FUNCTION.
