Tema 13 Flashcards
Division of the NS
Central NS (CNS)
Formed by the brain and spinal cord
Peripheral NS (PNS):
Formed by the cranial and spinal nerves, which contain motor and sensory neurons.
It connects the CNS with muscles, glands and sensory receptors.
Hierarchy of the NS
Most complex system of the organism.
Formed by neurons and glial cells
Hierarchical structure:
- Basic level: spinal cord and brainstem
-Medium level: midbrain, thalamus and hypothalamus
-Higher level: frontal cortex
SPINAL CORD
Part of the CNS
- Most caudal/lower part
- 31 pairs of spinal nerves
- It receives and processes the sensory information
- It contains motor neurons
BRAINSTEM
Part of the CNS
It receives sensory information from the head through the cranial pairs and controls the head muscles through them (motor control)
It regulates the levels of wakefulness and attention (Ascending Reticular Activating System; ARAS)
The brainstem consists of three parts:
- bulb
- pons/bridge
-midbrain
Parts of the brainstem
Spinal bulb
Centers responsible for vital autonomic functions (digestion, respiration, heart rate …)
Protuberance (pons)
Receives movement information, from the cortex to the cerebellum.
Midbrain/ mesencephalon
Controls sensory and motor functions (movement of the eyes, coordination of visual and auditory reflexes).
Cerebellum
Modulates voluntary movement, coordinates posture and balance and participates in the learning of motor skills.
Diencephalon
Formed by thalamus and hypothalamus (SNC)
Hypothalamus
It regulates:
* autonomic nervous system
* hormonal secretion
* various habits
* cardiac rhythms
* body temperature…
Thalamus
Processes and distributes most of the sensory and motor information that reaches the cerebral cortex from the rest of the SN.
Brain hemispheres
Cerebral cortex: control of the functioning of the rest of nerve centers; receives
the sensations; develops conscious responses to those situations
Basal ganglia: Participate in motor regulation.
Hippocampus: Memory storage
Amygdala: Coordinates vegetative and endocrine responses with emotional states.
PARTS OF THE PNS
Sensory NS:
*Neurons of the special and somatic senses. * Autonomic sensory neurons.
Motor NS:
*Somatic: impulses to the voluntary skeletal muscles.
* Autonomous (sympathetic and parasympathetic): impulses to smooth
muscle, myocardium and glands.
Enteric NS:
*Controls the gastrointestinal tract, almost independent of another NS division
Functional organisation of the NS
- Afferent systems
-Sensory information is usually classified according to the type of stimuli (thermoreceptor, mechanoreceptor..)
-The information that comes from the sensory receptors is processed mainly in the cerebral cortex (previously it has passed through a synapse in the thalamus), but also in the medulla and stem of the brain. - Efferent systems
-The somatic motor NS controls the skeletal muscle system (voluntary movements) through the motor nerves.
-The autonomic NS controls the smooth and cardiac muscles and the glands. –> sympathetic and parasympathetic
LEVELS OF INTEGRATION OF THE CNS
- Spinal level
The spinal cord is a communication channel between the periphery and the brain.
In addition, it is the integrating center of some simple reflexes: - Myotatic reflex.
- Flexor reflex.
- Some walking movements.
The upper levels of the NS regulate the spinal centers to control their functions
2.Low brain level
Formed by bulb, protuberance, midbrain, hypothalamus, thalamus and basal ganglia.
They coordinate numerous functions related to the control of subconscious activity:
1. Blood pressure.
2. Breathing.
3. Salivation.
4. Sexual activity
5. Reactions to pain.
6. Balance…
3.Upper cerebral or cortical level
It is the main integrating area of the NS.
It is essential for the processes of thoughts, learning and memory.
Emotions are generated in the cortex.
It never works alone, but in relation to the lower levels of the NS, turning its functions into very specific and precise operations.
NEUROENDOCRINE REGULATION
The products of the hypothalamus-pituitary gland regulate the function of the reproductive, thyroid, adrenal glands, and also control somatic growth, lactation and water metabolism.
Interrelations between the various hypothalamic regulatory centers, their affections from various parts of the brain and their efferences to the pituitary gland.
§ Sleep, pain, stress, energy needs, temperature and certain signals of the autonomic nervous system, as well as other factors, influence the functioning of the pituitary gland
NERVOUS VS ENDOCRINE SYSTEM
NS / ES
Neuronal network / Glands
Locally released neurotransmitter/ Hormone distributed by the blood
Quick/ Slow
Short duration / Long duration
Action close to the release site/
Action far from the release site
Protection of the CNS
The CNS is protected by:
A. Bones of the skull and spine. B. Meninges.
C. Cerebrospinal fluid (CSF).
CNS is surrounded by 3 protective layers of connective tissue called meninges (cranial and spinal):
1. dura mater, on the outside
2. arachnoid, in the middle
3. pia mater, inside
BRAIN CIRCULATION
The blood reaches the brain mainly through the internal carotid and vertebral arteries (they join forming the polygon of Willis at the base of the brain).
It returns by internal jugular to the heart.
It only accounts for 2% of body weight, but the brain uses 20% of oxygen and glucose.
The interruption of the blood supply during 1-2 minutes deteriorates the neuronal function, and more than 4 can generate permanent damage.
