The (neuro)vascular system as a key brain-body interface Flashcards
How is the connection of the CNS to the wider world usually considered?
In simple terms –> sensory input and motor output
How are the connections between the CNS and the wider world implemented?
By the peripheral nervous system
What are the divisions of the peripheral nervous system?
Sensory (afferent) division + motor (efferent division)
Motor division divides into autonomic and somatic nervous system
Autonomic nervous system divides into sympathetic division and parasympathetic division
What is the function of the autonomic nervous system?
Controls involuntary responses
What is the function of the somatic nervous system?
Controls voluntary movement
What is the function of the sympathetic division?
Mobilises body systems
Fight or flight response
What is the function of the parasympathetic division?
Conserves energy
Rest and digest responses
How else does the brain and body communicate?
The vascular system and the blood brain barrier
What is meant by the hungry brain?
The brain is a highly demanding organ which is very costly to maintain
Brain uses 1.5 pints of blood per minute
Brain is 2% of body mass but demands approx 20% of cardiac output
Limited storage capacity so therefore need an excellent supply chain - each neuron effectively has its own supply capillary
How does the brain manage supply with changing demands?
Neurovascular coupling
== Delivery of nutrients to the brain tissue, removal of waste products
What is the neurovascular unit?
A group of closely related cells and extracellular matrix components that function in the homeostatic haemodynamic response of NVC
Provides the blood-brain barrier
What cells are in the neurovascular unit?
Neurons
Astrocytes
Pericytes
Vascular cells (endothelial cells)
What molecules can pass through the BBB through simple diffusion?
SMALL MOLECULES
Water
Oxygen
Carbon dioxide
Ammonia (NH3)
Ethanol
LIPOPHILIC SUBSTANCES
Steroid hormones
What molecules require special transport proteins to travel across the BBB?
Glucose (GLUT-1)
Amino acids
What is a hormone?
A signalling molecule that is transported between organs of the body by the vascular system and coordinate different functions in your body
What are hormones essential for?
The regulation of development, physiology and behaviour
What system in the body produces hormones? What structures make up this system?
Produced by many organs of the endocrine system
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Pancreas
What are the main functions of hormones?
- Regulate physiology across the whole body in accordance with motivational states such as arousal, aggression, hunger, fear and fatigue
- Regulate many processes including, digestion, metabolism, respiration, tissue function, sensory perception, sleep, excretion, lactation, growth and development, movement, reproduction
What are the common features of hormones?
Feedforward and feedback signalling
Bidirectional influences between body and brain
Explain the complex feedback architecture of the hormone system
Disturbance or feedback provides an input into the endocrine system
Measuring element and set point (e.g., body temp) creates error signal
Error signal inputs the controller which sends a command to the effectors
Effector provides feedback to the input
What are the structures of the endocrine system?
Hypothalamus
Pituitary gland
Pineal gland
Thyroid gland
Parathyroids
Adrenal glands
Pancreas
Reproductive system (testis and ovaries)
What is the function of the hypothalamus?
Brain region controlling the pituitary gland
Releasing hormones that direct other hormones or other glands to manage other bodily functions like sleep, mood, muscle and bone growth and sexual drive
What is the function of the pituitary gland?
Secretes many different hormones, some of which affect other glands
Controls metabolism, growth, sexual maturation, reproduction, blood pressure and many other vital physical functions and processes
What is the function of the thyroid gland?
One of its main functions is to produce hormones that help regulate the body’s metabolism (the process that turns food into energy)
What is the function of the parathyroids?
Helps regulate levels of calcium in the blood
What is the function of the adrenal glands?
Produces hormones that help regulate your metabolism, immune system, blood pressure, response to stress and other essential functions
Main function - trigger the fight or flight response
What is the function of the pancreas?
Regulates the level of sugar in the blood
What are the major differences between neurotransmitters and hormones?
NEUROTRANSMITTERS
- Fast acting
- Act over short distances
- Restricted to nerve pathways
- Relatively short duration of action
- Digital action (via neuronal signalling)
- Tend to have more targeted actions
HORMONES
- Slow acting
- Act over long distances
- Travel anywhere via circulatory system
- Relatively long duration of action
- Analogue (continuously variable)
- Tends to have more diffuse actions
Hormones are thus able to not only access parts of us that neurotransmitters cannot reach, but are also able to offer a qualitatively different mechanism of signalling that may complement that orchestrated by the CNS/PNS
What is the hypothalamus considered as in the hormone system?
Master controller of the control hierarchy?
What are the inputs and outputs of the hypothalamus?
Receives contextual information (cerebral cortex, amygdala, hippocampal formation)
+
Receives sensory inputs (visceral and somatic sensory pathways, chemosensory and humoral signals)
Hypothalamus compares input to biological set points and creates visceral motor, somatic motor, neuroendocrine, behavioural responses
What are the anterior pituitary hormones?
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Thyroid-stimulating hormone (TSH)
Prolactin (PRL)
Growth hormone (GH)
Adrenocorticotropic hormone (ACTH)
What hormones stimulates production of sex hormones by gonads?
Releasing hormone (hypothalamus) = Gonadotropin-releasing hormone (GnRH
Pituitary hormone =
Luteinizing hormone (LH)
Target =
Reproductive system
What hormone stimulates production of sperm and eggs?
Releasing hormone (hypothalamus) = Gonadotropin-releasing hormone (GnRH)
Pituitary hormone =
Follicle-stimulating hormone (FSH)
Target =
Reproductive system
What hormone stimulates the release of thyroid hormone?
Releasing hormone (hypothalamus) =
Thyrotropin-releasing hormone (TRH)
Pituitary hormone =
Thyroid-stimulating hormone (TSH)
Target =
Thyroid gland
What hormone promotes milk production?
Releasing hormone (hypothalamus) =
Prolactin-releasing hormone (PRH)
Pituitary hormone =
Prolactin (PRL)
Target =
Mammary glands
What is prolactin-releasing hormone (PRH) inhibited by?
Prolactin-inhibiting hormone (PIH)
What hormones induces targets to produce insulin-like growth factors?
Releasing hormone (hypothalamus) =
Growth hormone-releasing hormone (GHRH)
Pituitary hormone =
Growth hormone (GH)
Target =
Liver, bone, muscles
What hormones induces targets to produce glucocorticoids which regulate metabolism and the stress response?
Releasing hormone (hypothalamus) =
Corticotrophin-releasing hormone
Pituitary hormone =
Adrenocorticotropic hormone (ACTH)
Target =
Adrenal glands
What are the posterior pituitary hormones?
Oxytocin (OT)
Vasopressin/anti-diuretic hormone (ADH)
What are the targets and effects of ADH?
Target =
Kidneys, sweat glands, circulatory system
Effects =
Water balance
What are the targets and effects of OT?
Target =
Female reproductive system
Effects =
Triggers uterine contractions during childbirth
How does the BBB effect the hormone highway?
The BBB is a target for circulating substances secreted by other tissues
Blood to brain passage of hormones across the BBB allows the brain to be an endocrine target
The BBB secretes substances into the circulation that affect other tissues
Blood to brain passage of substances across the BBB allows the brain to act as an endocrine secretory tissue
