Week 11: Brain and Behaviour Flashcards
What is neural control /regulation?
Functional interactions between networks of neurons that regulate/control a behaviour/function
How the brain controls respiratory rate
Control by the brainstem of intercostal muscles
- Pons and medulla
Basal breathing
▪ Dorsal respiratory region of the medulla
▪ Inspiratory neurons spontaneously fire (no signals needed)
▪ Signals through C3,4,5 (spine) to innervate the diaphragm via phrenic nerve (only the diaphragm is needed for basic breathing) - controlled at a basal level
Can also consciously control breathing via intercostal muscles, In pons (pneumo taxic area)
When more air is needed…
Innervation of external intercostal muscles by medulla to further lift ribs = higher volume = more air
Can do it peripherally (the heart detects changes in O2/Co2 = sends signals to medulla
What other examples of neural control can you think of?
- Thermoregulation
- Heart rate
- Emotion
- Heart rate
Recap: Diencephalon
▪ Division of forebrain
▪ Located between telencephalon & mesencephalon (midbrain)
▪ Surrounding the third ventricle
▪ Contains the thalamus and the hypothalamus
Hypothalamus structure
▪ Small but important
▪ Below thalamus at base of brain
▪ Ventral part of diencephalon
▪ Consists of a group of nuclei & fibre tracts
▪ ANS (Autonomic Nervous System)
▪ Endocrine system
Hypothalamus function
▪ Hormone production
▪ Primary function is homeostasis
▪ Organizes survival behaviours
Homeostasis
is the state of steady internal, physical, and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and includes many variables
Hypothalamus function pt2
▪ Contains “biological clock” which regulates certain body functions that vary:
* Daily (diurnally)
* Over a period of many days
▪ Involved in control of emotional expression, such as rage, pleasure & fear ▪ Controls autonomic NS ▪ Controls endocrine system * via the pituitary gland
(Fighting, fleeing, feeding, f…)
Pituitary gland
▪ Attached to base of hypothalamus via pituitary stalk
▪ Two main lobes (anterior & posterior)
▪ Anterior pituitary gland is considered “master” gland
Anterior pituitary gland: ‘master gland’
○ Growth hormone
○ FSH
○ Luteinising hormone
○ Adrenocorticotrophic hormone
○ Thyroid-stimulating hormone
- Prolactin
Posterior pituitary gland:
○ Oxytosin
Vasopressin
Hypothalamus control of pituitary gland
▪ Communicates with both anterior and posterior pituitary gland to alter hormone secretion:
* Anterior pituitary gland (indirect) = hormones
- Posterior pituitary gland (direct) = synaptic transmission
Anterior pituitary gland Indirect control - Hormones
▪ Specialised neurons in hypothalamus secrete hormones
▪ Hormones travel to anterior pituitary via blood vessels
▪ Hormones secreted from hypothalamus stimulate hormone release from anterior pituitary gland
Hypothalamic Pituitary Axis (HPA): The stress response
▪ Paraventricular nucleus secretes corticotropin-releasing hormone (CRH)
▪ Stimulates anterior pituitary gland to release adrenocorticotropic hormone (ACTH) ▪ Enters blood and stimulates adrenal cortex (adrenal glands) to release cortisol
▪ The stress response
What are the effects of cortisol exposure: short term
Short term, stress can be adventageous
What are the effects of cortisol exposure: Long-term
○ When long-term, damages organs & cells around body
○ Cortisol, epinephrine and adrenaline ○ Adrenaline = increased blood pressure ○ Cortisol = effects function of inner lining of blood vessels = cholesterol build up ○ Can effects gut bacteria & digestive system ○ Cortisol can increase food cravings/ appetite as want to increase energy - Fat is an organ that releases cytokines that can increase risk of diseases
○ Immune cells effected = more succeptible to infection
Chronic stress can also lead to acne, hair loss, headaches, muscle tension, loss of concentration…
Cortisol and epigenetics
▪ Stress responses seem to be altered by environment and epigenetics
(epigenetics - have genetic code for certain phenotypes, but these can be expressed/ repressed due to the environment)
Alteration in the expression of genes due to nurture
Epigenetics: Stress and rat studies
- Offspring of nurturing mothers more resilient to stress
* Offspring of negligent mothers more affected by stress
- Effect seen in future generations
Chronic stress: Memory
- Cortisol release (short term) = stress response, acutely can be good & increase memory / performance
- Chronic stress = memory deteriorate. Ability to control your stress reduces
Causes brain to shrink in size (loss of synaptic connections in neurones with cortisol)
- Chronic stress = memory deteriorate. Ability to control your stress reduces
Can the damage of stress/ cortisol be undone?
Many ways to reverse what stress/ cortisol does = exercise and meditation
Posterior pituitary gland
Direct control – Synaptic transmission
▪ Considered an extension of hypothalamus ▪ Hypothalamus actually produces the posterior pituitary hormones & directly controls their secretion ▪ Neurons in hypothalamus have axons which extend down pituitary stalk and end in posterior pituitary gland
Sexual behaviour: Brain regions
▪ Spinal areas involved in sexual behaviour – Lumbar region
Both in hypothalamus:
▪ Medial Preoptic area – Males stimulated mostly
▪ Ventromedial nucleus of hypothalamus (VMH) - Females stimulated mostly
Medial Amygdala received chemosensory info from the vomeronasal system and somatosensory info from genitals
▪ Mediates signals to midbrain and medulla
(can also get sensory info from smells, e.g. studies on pheromones)
Medial Preoptic Area (MPA)
(for males)
- destruction abolishes sexular beh
- prenatal stress = decrease size = less sexual beh
- injection of testosterone enhances sexual beh of castrated rats
Ventromedial Nucleus of Hypothalamus (VMH)
(for females)
- destruction = abolished sexual beh
- neurons contain estrogen and progesterone receptors
- injection of estradiol and progesterone enhances sexual beh of rats
Role of the homunculus in women:
- associated with sensitivity
- represents the connection between different body parts and areas of the brain
Studies on Humans - Georgiadis
▪ Work on sexually impulsive men show weaker areas of connectivity between the prefrontal cortex and amygdala.
(links to inhibition of decisions?)
(Suggests prefrontal cortex reduces sexual drive.)
Georgiadis looked at how Biological, Physiological and Social contexts interact and moderate regional brain activity
Situational factors
Contextual cues
- identified 3 different phases
(expectation, consummation, satiety)
Georgiadis: Situational factors
inner thigh (got a confederate to rub men’s inner thigh - depending on the picture of the person put in front of them, e.g. male or female, they either got turned on or not. The confederate remained the same)
Georgiadis: Contextual cues
rats in jackets (Put in jackets and then stimulated the rats - learned through classical conditioning what the jacket meant. When went to stimulate them without the jacket on, they did not get aroused)
Area of perfrontal cortex associated with sexual deviance?
Orbitofronal area of prefrontal cortex is what is associated with sexual deviance - without it, there is less ‘control’ of desires.
Neural regulation of sexual behaviour circuit includes:
▪ limbic (hypothalamus, hippocampus, and amygdala) (ANS)
▪ paralimbic areas (ACC, frontal lobe, and insula), (linked to somatosensory area) (insula region linked to self awareness/ self-consciousness during sex) ▪ the associative cortices (inferior temporal and occipital cortices),
▪ other subcortical and cortical sensory relays (thalamus and secondary somatosensory cortex)
Eating behaviour: Role in hunger and satiety: brain region?
Hypothalamus
What part of hypothalamus triggers hunger?
Lateral hypothalamus
What part of hypothalamus triggers satiety
Ventromedial hypothalamus
Reading: Hypothalamus location & role
- Part of the Diencephalon (the hypothalamus and thalamus make up the basal ganglia)
- Controls the ANS & endocrine system & survival beh
- The hypothalamus controls many behaviors, such as drinking and sleeping.
A special system of blood vessels directly connects the hypothalamus with the anterior pituitary gland. The hypothalamic hormones are secreted by specialized neurons called neurosecretory cells. These hormones stimulate the anterior pituitary gland to secrete its hormones
Male sexual beh: Circuits of neurones in the lumbar section of the spinal cord control what?
Erection and ejaculation
The brain has excitatory or inhibitory control over this
Male sexual beh: Brain region
The MPA (Medial preoptic area) (in the forebrain) controls male sexual beh
The MPA also receives somatosensory information from the genitals, the central tegmental field of the midbrain, and the medial amygdala.
Male beh: sexually dimorphic nucleus (SDN)
A nucleus in the preoptic area that is much larger in males than in females; first observed in rats; plays a role in male sexual behavior.
Male beh: The nucleus paragigantocellularis, nPGi
has inhibitory effects on spinal cord sexual reflexes, so one of the tasks of the pathway V originating in the MPA is to suppress this inhibition. The MPA suppresses the nPGi directly through an inhibitory pathway and also does so indirectly by inhibiting the activity of the PAG, which normally excites the nPGi.
Female sexual beh: region
- Similar to males, the spinal areas involved in sexual behavior span the lumbar region
- stimulation of the ventromedial nucleus facilitates female sexual behavior
Female beh: role of medial amygdala
sends efferent axons to ventromedial nucleus of the hypothalamus
Reading: Hunger: What are the appetite-inducing chemicals?
melanin-concentrating hormone (MCH) and Orexin:
“Appetite-inducing chemicals”
the neurotransmitters found in a system of lateral hypothalamic neurons that stimulate appetite and reduce metabolic rate.
(aim to increase energy stores)
Reading: Satiety: hormone involved
leptin, a hormone secreted by well-fed adipose tissue, suppresses eating and raises the animal’s metabolic rate.
